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17 Sep 1990

Volume 57, Issue 12, pp. 1179-1273

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Low‐threshold continuous‐wave room‐temperature operation of AlxGa1−xAs/GaAs single quantum well lasers grown by metalorganic chemical vapor deposition on Si substrates with SiO2 back coating

T. Egawa, H. Tada, Y. Kobayashi, T. Soga, T. Jimbo, and M. Umeno

Appl. Phys. Lett. 57, 1179 (1990); http://dx.doi.org/10.1063/1.103519 (3 pages) | Cited 20 times

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We demonstrate the first room‐temperature low‐threshold continuous‐wave (cw) operation of Al0.3Ga0.7As/GaAs single quantum well (SQW) heterostructure lasers grown by metalorganic chemical vapor deposition (MOCVD) on Si substrates using techniques of SiO2 back coating and thermal cycle annealing. The all‐MOCVD‐grown SQW lasers on GaAs/Si with etch pit density of 1.5× 107 cm−2 have threshold current as low as 55 mA (1.41 kA/cm2) under cw at room temperature. The SiO2 back coating is effective to obtain excellent current‐voltage characteristics. Thermal cycle annealing is also found to improve the crystallinity of GaAs/Si and to contribute to room‐temperature cw operation of the lasers on Si substrates.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
85.60.Jb Light-emitting devices

Continuous‐wave trio upconversion laser

Ping Xie and Stephen C. Rand

Appl. Phys. Lett. 57, 1182 (1990); http://dx.doi.org/10.1063/1.103520 (3 pages) | Cited 15 times

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We report operation of what we believe is the first continuous‐wave laser which relies exclusively on cooperative upconversion by coupled ion trios to achieve population inversion.
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42.55.Ah General laser theory
42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.45.+h Stimulated emission

Picosecond acoustic pulse reflection from a metal‐metal interface

Kathryn A. Svinarich, W. J. Meng, and G. L. Eesley

Appl. Phys. Lett. 57, 1185 (1990); http://dx.doi.org/10.1063/1.103521 (3 pages) | Cited 8 times

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Picosecond duration laser pulses are used to generate ultrashort acoustic pulses in a bilayer metal film. Time‐resolved transient piezoreflectance measurements permit the observation of acoustic reflections from a metal‐metal interface within the film, as well as reflections from the film‐substrate interface. We show that our measurements are well described by an abrupt interface model of acoustic mismatch.
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62.65.+k Acoustical properties of solids
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
68.60.Bs Mechanical and acoustical properties

Spatially resolved ion velocity distributions in a diverging field electron cyclotron resonance plasma reactor

Dennis J. Trevor, Nader Sadeghi, Toshiki Nakano, Jacques Derouard, Richard A. Gottscho, Pang Dow Foo, and Joel M. Cook

Appl. Phys. Lett. 57, 1188 (1990); http://dx.doi.org/10.1063/1.103482 (3 pages) | Cited 29 times

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Electron cyclotron resonance plasma sources are gaining widespread use in plasma processing because they offer high ion flux with controllable energy and thereby high etching and deposition rates with minimal damage. However, it is unclear how ion energy distributions evolve from source to wafer as a function of plasma parameters such as pressure, microwave power, and magnetic field strength. Therefore, we used Doppler broadened and shifted laser‐induced fluorescent line profiles to measure Ar+ metastable ion velocity distributions downstream from a divergent magnetic field electron cyclotron resonance source. Spatially resolved distributions, measured at positions above and across a wafer platen, differ markedly from shifted Maxwell–Boltzmann functions. Ions are accelerated along the magnetic field direction by a weak (∼0.5 V/cm), ambipolar electrostatic field. The ion energy component perpendicular to the electric field corresponds to a temperature of only 0.46±0.10 eV. On the edges of the platen, the magnetic and electrostatic fields diverge causing angled acceleration of ions.
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81.15.Np Solid phase epitaxy; growth from solid phases
61.72.uf Ge and Si
66.30.J- Diffusion of impurities

In‐plane anisotropy in batch‐produced Langmuir–Blodgett films: Side‐by‐side and face‐to‐face arrays

Yuka Tabe, Keiichi Ikegami, Shin‐ichi Kuroda, Kazuhiro Saito, Mitsuyoshi Saito, and Michio Sugi

Appl. Phys. Lett. 57, 1191 (1990); http://dx.doi.org/10.1063/1.103483 (3 pages) | Cited 3 times

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In‐plane anisotropy of Langmuir–Blodgett (LB) films is affected by the arrangement of substrates when many samples are batch produced in one single trough. We examined the dichroic behavior for two different cases of the batch production. In the case of substrates aligned side by side, the dichroic behavior is similar to that in the single‐substrate production and agrees with the flow orientation model. In the face‐to‐face case, however, the tendency is quite different from both the single‐substrate production and the side‐by‐side case, clearly deviating from the theoretical predictions. This discrepancy is suggested to be due to a dead water area which should be formed around the stagnation point.
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78.66.Qn Polymers; organic compounds
46.40.-f Vibrations and mechanical waves
83.50.-v Deformation and flow
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes

Fluorination of diamond (100) by atomic and molecular beams

Andrew Freedman and Charter D. Stinespring

Appl. Phys. Lett. 57, 1194 (1990); http://dx.doi.org/10.1063/1.104097 (3 pages) | Cited 32 times

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Diamond (100) substrates have been fluorinated under ultrahigh vacuum conditions with both atomic and molecular fluorine. X‐ray photoelectron spectra of the resulting samples indicate that atomic fluorine, F, reacts efficiently at 300 K producing a saturation coverage of about three quarters of a monolayer (one monolayer ≂1.6×1015 cm−2) after 40 monolayers exposure. The carbon fluoride adlayer is thermally stable to 700 K but slowly desorbs at temperatures above this. In contrast, molecular fluorine, F2, reacts quite slowly; a saturation coverage of less than one fifth of a monolayer is achieved after several hundred monolayer exposure to F2 at temperatures from 300 to 700 K. Diamond surfaces saturated with fluorine atoms showed no loss of fluorine after sequential exposure to beams of H2 and O2 at temperatures between 300 and 700 K.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Bias stress‐induced instabilities in amorphous silicon nitride/hydrogenated amorphous silicon structures: Is the ‘‘carrier‐induced defect creation’’ model correct?

A. V. Gelatos and J. Kanicki

Appl. Phys. Lett. 57, 1197 (1990); http://dx.doi.org/10.1063/1.103484 (3 pages) | Cited 39 times

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The effects of positive and negative bias stress on hydrogenated amorphous silicon nitride/hydrogenated amorphous silicon (a‐SiNx:H/a‐Si:H) structures are investigated as a function of stress time, and stress temperature. It is shown that bias stress induces a parallel shift of the capacitance voltage (C‐V) characteristics. The direction of the C‐V shift depends on the sign of the applied stress voltage, while the magnitude of the C‐V shift depends on stress time and temperature in a manner which is identical to that observed in a‐Si:H thin‐film transistors. In addition, it is shown that positive bias stress increases the number of localized states in the a‐Si:H mobility gap, but negative bias stress does not. However, the observed increase cannot account for the corresponding C‐V shift. These results lead us to conclude that the C‐V shift is not induced by dangling bond defects in a‐Si:H but rather by carrier trapping in the insulator.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects
85.30.De Semiconductor-device characterization, design, and modeling

Layer thickness calculations for silicon‐on‐insulator structures formed by oxygen implantation

U. Bussmann and P. L. F. Hemment

Appl. Phys. Lett. 57, 1200 (1990); http://dx.doi.org/10.1063/1.104227 (3 pages) | Cited 9 times

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A new computer program enables the evolution of oxygen distributions in separation by implanted oxygen (SIMOX) substrates to be simulated during implantation and also after high‐temperature annealing. The positions of the Si/SiO2 interfaces have been calculated for implantation energies of 150 and 200 keV. Theoretical results are in good agreement with experimental data over a wide range of fluences. It is found that the use of multiple implantation and annealing cycles, in comparison with a single implantation stage, shifts the buried oxide layer towards the surface.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
68.55.Nq Composition and phase identification

Gallium desorption from GaAs and (Al,Ga)As during molecular beam epitaxy growth at high temperatures

E. M. Gibson, C. T. Foxon, J. Zhang, and B. A. Joyce

Appl. Phys. Lett. 57, 1203 (1990); http://dx.doi.org/10.1063/1.103485 (3 pages) | Cited 16 times

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Direct measurements of the desorption rate of gallium from GaAs and (Al,Ga)As during growth by molecular beam epitaxy at high temperatures have been made by modulated beam mass spectrometry. The activation energy for desorption is dependent upon the nature of the site from which the gallium is lost. From free gallium atoms not incorporated into the lattice, behavior similar to that encountered under equilibrium conditions for gallium over gallium or gallium over GaAs is observed. For gallium lost from the GaAs lattice the apparent activation energy is higher and is influenced by the arsenic flux reaching the surface.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

New insights on the electronic properties of the trivalent silicon defects at oxidized 〈100〉 silicon surfaces

Dominique Vuillaume, Didier Goguenheim, and Gilbert Vincent

Appl. Phys. Lett. 57, 1206 (1990); http://dx.doi.org/10.1063/1.103486 (3 pages) | Cited 22 times

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We perform a deep level transient spectroscopy (DLTS) measurement of the band‐gap energy distribution of the trivalent silicon defects (Pb centers) on as‐oxidized 〈100〉 silicon wafers. By comparison with the 〈111〉 silicon surface, we isolate the energy distribution of the Pb1 center. Its acceptor level is found at 0.42 ± 0.02 eV from the conduction band while the acceptor level for the 〈100〉 Pb0 center is found at 0.22 ± 0.01 eV, a value smaller than at the 〈111〉 surface (0.33 ± 0.01 eV). We obtain new results about the capture cross sections of the 〈100〉Pb centers by energy‐resolved DLTS trap filling experiments. The electron capture cross section of 〈100〉Pb1 is determined for the first time (5×10−16 cm2), while the electron capture cross section for 〈100〉 Pb0 (8×10−15 cm2) is found to be in agreement with earlier results.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.61.Ng Insulators

Lateral quantum well wires fabricated by selective metalorganic chemical vapor deposition

Takashi Fukui, Seigo Ando, and Yoshino K. Fukai

Appl. Phys. Lett. 57, 1209 (1990); http://dx.doi.org/10.1063/1.103487 (3 pages) | Cited 25 times

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GaAs quantum wires of a new type are fabricated on {110} crystallographic facets perpendicular to the (111)B substrates by selective area growth using metalorganic chemical vapor deposition. First, rectangular‐shaped AlGaAs layers are grown on a SiO2 stripe‐masked GaAs (111)B substrate at a high growth temperature. Next, n‐AlGaAs/GaAs modulation‐doped structures are laterally grown on {110} sidewalls at a low growth temperature. The channel width of the one‐dimensional electron gas can be exactly controlled by the thickness of the first rectangular AlGaAs layer. The existence of the quasi‐one‐dimensional electron gas on {110} sidewalls is confirmed by the orientation dependence of the Shubnikov‐de Hass oscillations. The advantage of this quantum wire structure is that there is no size fluctuation which is usually present when dry etching processes are used. Other applications of this selective growth on masked substrates, such as lateral superlattices, are also discussed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.Ey III-V semiconductors

Fabrication of ultrafine gratings on GaAs by electron beam lithography and two‐step wet chemical etching

T. Katoh, Y. Nagamune, G. P. Li, S. Fukatsu, Y. Shiraki, and R. Ito

Appl. Phys. Lett. 57, 1212 (1990); http://dx.doi.org/10.1063/1.103488 (3 pages) | Cited 5 times

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50 nm period gratings were produced on thick GaAs substrates by using electron beam lithography and two‐step wet chemical etching. The size was very close to the theoretical limit of the electron beam lithography. For transferring such a fine grating onto GaAs, a two‐step wet chemical etching method was developed, where a H2SO4‐H2O2‐H2O system is first used to roughly etch the oxygen and carbon‐contaminated GaAs surface, followed by surface planarization with a Br‐CH3OH system.
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85.40.Hp Lithography, masks and pattern transfer
81.65.-b Surface treatments
42.79.Dj Gratings

Studies of picosecond carrier dynamics in polysilane alloys: Evidence for geminate recombination in small hydrogenated amorphous silicon clusters

S. G. Han, B. C. Hess, G. S. Kanner, Z. V. Vardeny, and S. Nitta

Appl. Phys. Lett. 57, 1215 (1990); http://dx.doi.org/10.1063/1.104228 (3 pages) | Cited 1 time

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The ultrafast photocarrier dynamics in polysilane alloys, amorphous (SiH2)n, has been studied using the picosecond photoinduced absorption (PA) technique. For excitation below the optical gap, the PA response decays exponentially and is faster at low temperatures. This is interpreted in terms of e‐h geminate recombination in the small clusters (∼10 Å) of a‐Si:H embedded in the polysilane matrix. The PA response with above‐gap excitation is similar to that of conventional a‐Si:H; it decays much slower in the form of a power law t −β (β<1), independent of spectral range between 1.4 and 2.2 eV. This shows that the e‐h distance after above‐gap photogeneration is larger than the size of the a‐Si:H clusters.
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72.80.Ng Disordered solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics

Electron focusing with multiparallel GaAs‐AlGaAs wires defined by damageless processing

F. Nihey, K. Nakamura, M. Kuzuhara, N. Samoto, and T. Itoh

Appl. Phys. Lett. 57, 1218 (1990); http://dx.doi.org/10.1063/1.103489 (3 pages) | Cited 17 times

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Magnetoresistance modulation, resulting from electron focusing, is investigated with multiparallel GaAs‐AlGaAs wires, which are defined by electron beam lithography and damageless wet‐chemical etching. Distinct focusing peaks in magnetoresistance are observed, although the samples have wires longer than a ballistic mean free path, which is derived from the focusing peak intensity. Specularity coefficient p for the etched region boundary is also obtained as p≊1 from the focusing peak ratio. The mechanism limiting ballistic transport in the electron focusing condition is discussed, based on the temperature and the electron density dependence of the peak intensity.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.Ey III-V semiconductors
81.65.-b Surface treatments

Complete planarization of via holes with aluminum by selective and nonselective chemical vapor deposition

Kazuo Tsubouchi, Kazuya Masu, Nobuyuki Shigeeda, Tatsuya Matano, Yohei Hiura, and Nobuo Mikoshiba

Appl. Phys. Lett. 57, 1221 (1990); http://dx.doi.org/10.1063/1.103490 (3 pages) | Cited 24 times

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We have developed a new controllable method of selective and nonselective deposition of high quality aluminum by low‐pressure chemical vapor deposition using dimethylaluminum hydride with hydrogen. At first, silicon dioxide via holes on silicon substrate were selectively filled with aluminum by thermal decomposition. Then, adding the plasma excitation for 1 min, the aluminum film began to deposit nonselectively on the silicon dioxide as well as the selectively deposited aluminum. Silicon dioxide via holes were completely planarized by the selective and nonselective deposition. The single‐crystal structure of aluminum deposited selectively on silicon was observed with a new scanning microreflection high‐energy electron diffraction microscope.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
68.55.-a Thin film structure and morphology

Tight‐binding analysis of the conduction‐band structure in quantum wires

T. Yamauchi, Y. Arakawa, and J. N. Schulman

Appl. Phys. Lett. 57, 1224 (1990); http://dx.doi.org/10.1063/1.103491 (3 pages) | Cited 8 times

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The tight‐binding method is applied, for the first time, to the analysis of the conduction‐band structure of GaAs‐Al0.4Ga0.6As quantum wires which are parallel to the [110] orientation. The results indicate that the effective mass of electrons parallel to the quantum wires is about 1.45 times as large as that of bulk GaAs. This increased effective mass reduces the electron mobility of the quantum wire at low temperature compared to the value which has been expected.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Optically induced restructuring of a hydrogenated amorphous silicon thin‐film surface

Joydeep Dutta and Gautam Ganguly

Appl. Phys. Lett. 57, 1227 (1990); http://dx.doi.org/10.1063/1.103492 (3 pages) | Cited 3 times

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Hydrogenated amorphous silicon thin films have been characterized using specular reflectance spectra. An ultraviolet light‐induced irreversible increase in reflectance has been attributed to changes in surface microstructure. These changes have been explained as being caused by phonons emitted during photocarrier thermalization. An irreversible increase of photoconductivity substantiates these observations.
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78.66.-w Optical properties of specific thin films
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
72.80.Ng Disordered solids

Defect states of amorphous Si probed by the diffusion and solubility of Cu

A. Polman, D. C. Jacobson, S. Coffa, J. M. Poate, S. Roorda, and W. C. Sinke

Appl. Phys. Lett. 57, 1230 (1990); http://dx.doi.org/10.1063/1.103493 (3 pages) | Cited 37 times

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The diffusivity and solubility of Cu impurities have been measured in different structural states of amorphous Si (a‐Si) formed by MeV Si implantation. The 2.2‐μm‐thick a‐Si layers were first annealed (structurally relaxed) at 500 °C and then implanted with 200 keV Cu ions, returning a 300‐nm‐thick surface layer to the as‐implanted state. After diffusion at temperatures in the range 150–270 °C, we observe solute partitioning at a sharp phase boundary between the annealed and Cu‐implanted layers, the partition coefficient being as large as 8.2±1.3. The diffusion coefficient in annealed a‐Si is 2–5 times larger than in as‐implanted a‐Si, with activation energies of 1.39±0.15 and 1.25±0.04 eV, respectively. The data show quite strikingly the role which defects can play in the a‐Si structure.
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71.55.Ht Other nonmetals
73.20.Hb Impurity and defect levels; energy states of adsorbed species
66.30.J- Diffusion of impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Does the two‐dimensional electron gas effect contribute to high‐frequency and high‐speed performance of field‐effect transistors?

M. Feng, C. L. Lau, V. Eu, and C. Ito

Appl. Phys. Lett. 57, 1233 (1990); http://dx.doi.org/10.1063/1.103494 (3 pages) | Cited 8 times

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We present experimental evidence that current gain cutoff frequency (ft) values equal to or greater than those achieved with high electron mobility transistors (HEMTs) and pseudomorphic HEMTs can also be achieved by ion‐implanted GaAs and InGaAs metal‐semiconductor field‐effect transistors. These measured ft results clearly suggest that the average electron velocity under the gate is determined primarily by the high‐field electron velocity rather than the low‐field electron mobility. Hence, we conclude that the transport properties of the two‐dimensional electron gas in HEMTs and pseudomorphic HEMTs do not make a significant contribution to the high‐frequency and high‐speed performance of these devices.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Fq High-field and nonlinear effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Monte Carlo simulation of mode‐locked semiconductor diode lasers

J. Werner and T. P. Lee

Appl. Phys. Lett. 57, 1236 (1990); http://dx.doi.org/10.1063/1.103495 (3 pages)

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We report on results of a Monte Carlo simulation that uses traveling‐wave equations for the optical field of mode‐locked diode lasers. The model includes effects of the spontaneous emission, the linewidth enhancement factor, and nonlinear gain. The results of the simulation agree with experimental observations such as the sublinear power versus current characteristics. According to this model the reduced power is a result of combined large‐signal effects. We propose to incorporate a frequency shifter into the cavity to improve the pulse energy and the use of available bandwidth.
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42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
42.82.-m Integrated optics

Relationship between thermal stress and structural properties of SrF2 films on (100) InP

R. Singh, R. P. S. Thakur, A. Katz, A. J. Nelson, S. C. Gebhard, and A. B. Swartzlander

Appl. Phys. Lett. 57, 1239 (1990); http://dx.doi.org/10.1063/1.103496 (3 pages) | Cited 3 times

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The measurement of thermal stress of SrF2 films on InP as a function of temperature is presented. The in situ and ex situ rapid isothermal annealed films have different values of thermal stress at room temperature and show entirely different behavior of thermal stress during heating and cooling cycles. X‐ray photoelectron spectroscopy measurements were used to characterize the surface of the SrF2 films as well as the SrF2/InP interface for both the ex situ and in situ annealed films. It is shown that the difference in the microstructure of in situ and ex situ rapid isothermal annealed SrF2 films on InP is indeed reflected in the significant difference in the thermal stress.
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62.20.M- Structural failure of materials
65.20.-w Thermal properties of liquids
65.40.gd Entropy
68.35.Md Surface thermodynamics, surface energies

Correlations between the interfacial chemistry and current‐voltage behavior of n‐GaAs/liquid junctions

Bruce J. Tufts, Louis G. Casagrande, Nathan S. Lewis, and Frank J. Grunthaner

Appl. Phys. Lett. 57, 1242 (1990); http://dx.doi.org/10.1063/1.103497 (3 pages)

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See Also: Erratum

Show Abstract
Correlations between the surface chemistry of etched, (100) oriented n‐GaAs electrodes and their subsequent photoelectrochemical behavior have been probed by high‐resolution x‐ray photoelectron spectroscopy. GaAs photoanodes were chemically treated to prepare either an oxide‐free near stoichiometric surface, a surface enriched in zero‐valent arsenic (As0), or a substrate‐oxide terminated surface. The current‐voltage (I‐V) behavior of each surface type was subsequently monitored in contact with several electrolytes.
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73.30.+y Surface double layers, Schottky barriers, and work functions
72.40.+w Photoconduction and photovoltaic effects
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Electric field dependent photocurrent and electroreflectance spectra of InGaAs/AlGaAs multiple strained quantum well structures

I. J. Fritz, T. M. Brennan, J. R. Wendt, and D. S. Ginley

Appl. Phys. Lett. 57, 1245 (1990); http://dx.doi.org/10.1063/1.103498 (3 pages) | Cited 11 times

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We present results on excitonic transitions and confinement at high electric fields from photocurrent and electroreflectance spectra of an In0.17Ga0.83As/Al0.3Ga0.7As strained quantum well structure fabricated into a Schottky barrier diode. Up to the highest field attained, 1.7×105 V/cm, we observe a well‐defined exciton line at the band edge (in contrast to data on similar GaAs/Al0.3Ga0.7As structures), a feature important for potential optoelectronic applications. At low fields, ‘‘allowed’’ (Δn=0) transitions dominate the photocurrent spectra, but with increasing field ‘‘forbidden’’ transitions (allowed because of reduced symmetry and valence‐band mixing) grow in intensity and eventually dominate the above‐gap response. In the electroreflectance spectra, the forbidden transitions are relatively strong, even at low field. The allowed above‐gap transitions nearly vanish at low temperature because of the small field dependence of the higher lying quantum well energy levels.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Pz Photoconduction and photovoltaic effects
78.20.Jq Electro-optical effects

Ultrathin oxide‐nitride‐oxide films

Z. A. Weinberg, K. J. Stein, T. N. Nguyen, and J. Y. Sun

Appl. Phys. Lett. 57, 1248 (1990); http://dx.doi.org/10.1063/1.103499 (3 pages) | Cited 21 times

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It is demonstrated that the thickness limit of a thin nitride film which can withstand reoxidation is reduced to about 3.5 nm when it is deposited in situ on a thin‐deposited oxide film. The deposited oxide apparently provides a better surface for nitride nucleation and initial growth. Using this finding an oxide‐nitride‐oxide (ONO) film as thin as 4.6 nm was fabricated and shown to have good electrical properties and low defect density. The current leakage through the film was close to the acceptable limit in dynamic‐random‐access‐memory technology. It was also found that electron trapping is substantially higher in ONO films produced by reoxidation than in films having a top deposited oxide.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
72.80.Sk Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

High sensitivity In0.53Ga0.47As/InP heterojunction phototransistor

L. Y. Leu, J. T. Gardner, and S. R. Forrest

Appl. Phys. Lett. 57, 1251 (1990); http://dx.doi.org/10.1063/1.103500 (3 pages) | Cited 4 times

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We describe both theoretical and experimental investigations of the effects of inserting a thin, low‐doped layer into the emitter of an InP/In0.53Ga0.47As heterojunction phototransistor (HPT). This high‐low emitter structure has improved sensitivity over conventional structures at low input optical power by decreasing the bulk recombination current at the heterointerface. Experimental data show that the photocurrent gain is independent of the incident optical power at high input powers, corresponding to a heterojunction ideality factor of 1. At low input power, the gain is found to have a small power dependence, with an ideality factor of 1.25. A current gain as high as 260 is obtained at an input power of only 40 nW. These results, which are consistent with numerical simulations of the HPTs, give direct evidence that bulk recombination in the space‐charge region at the emitter/base junction is the major source of recombination current for an InP/In0.53Ga0.47As HPT.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
85.60.-q Optoelectronic devices
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