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3 Apr 1995

Volume 66, Issue 14, pp. 1715-1850

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Angular selective transmittance through electrochromic tungsten oxide films made by oblique angle sputtering

D. Le Bellac, A. Azens, and C. G. Granqvist

Appl. Phys. Lett. 66, 1715 (1995); http://dx.doi.org/10.1063/1.113343 (2 pages) | Cited 20 times

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Tungsten oxide films were made by magnetron sputtering with a large angle between the substrate normal and the direction of the deposition flux. Scanning electron microscopy displayed a microstructure composed of inclined columns. Spectrophotometric measurements on films with different amounts of electrochemically intercalated Li+ ions showed pronounced angular selective transmittance together with electrochromism. © 1995 American Institute of Physics.
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81.15.Cd Deposition by sputtering
78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Gain controlled vertical cavity surface emitting lasers coupled with intracavity in‐plane lasers

D. B. Shire, C. L. Tang, M. A. Parker, P. D. Swanson, and J. S. Kimmet

Appl. Phys. Lett. 66, 1717 (1995); http://dx.doi.org/10.1063/1.113344 (3 pages) | Cited 7 times

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We report the observation of optical control of the stimulated emission of a vertical cavity surface emitting laser (VCSEL) by an intra‐cavity coupled in‐plane laser. Depending on the overlap between the two gain regions, greater than 70% change in threshold current to complete quenching of the VCSEL, is observed. The combined device offers a wide variety of potential applications for integrated, all‐optical logic devices and optical interconnects between signal planes. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.Gw Other integrated-optical elements and systems

Measurement of internal quantum efficiency and losses in vertical cavity surface emitting lasers

D. V. Kuksenkov, H. Temkin, and S. Swirhun

Appl. Phys. Lett. 66, 1720 (1995); http://dx.doi.org/10.1063/1.113345 (3 pages) | Cited 11 times

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A new experimental technique for the measurement of intrinsic parameters of vertical cavity surface emitting lasers is suggested. Using an external cavity with variable reflectivity we measure the internal quantum efficiency of ηi=0.6 and internal losses of αi=10 cm−1 in a gain guided AlGaAs/GaAs laser operating at 850 nm. In addition, transparency current of I0∼0.46×Ith is obtained, in excellent agreement with a direct measurement. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Lasing characteristics of low threshold microcavity lasers using half‐wave spacer layers and lateral index confinement

D. L. Huffaker, J. Shin, and D. G. Deppe

Appl. Phys. Lett. 66, 1723 (1995); http://dx.doi.org/10.1063/1.113346 (3 pages) | Cited 16 times

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Data are presented characterizing threshold and transverse mode behavior of microcavity lasers, which use a half‐wavelength cavity spacer layer surrounding a single quantum well active region. Selective conversion of AlAs into AlxOy is used to define lateral device dimensions of 2, 5, and 8 μm. Initial results demonstrate a continuous‐wave room‐temperature lasing threshold current of 97 μA for a 2 μm device and 220 μA for an 8 μm device. We show that lasing operation is influenced by the AlxOy located only 200 Å from the quantum well. © 1995 American Institute of Physics.  
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Nonlinear optical properties of textured strontium barium niobate thin films prepared by metalorganic chemical vapor deposition

M. J. Nystrom, B. W. Wessels, W. P. Lin, G. K. Wong, D. A. Neumayer, and T. J. Marks

Appl. Phys. Lett. 66, 1726 (1995); http://dx.doi.org/10.1063/1.113347 (3 pages) | Cited 20 times

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Highly textured strontium barium niobate thin films were deposited in situ by low pressure metalorganic chemical vapor deposition. [001]‐oriented strontium barium niobate films on single crystal (100) magnesium oxide substrates were obtained at a growth temperature of 800 °C. Second‐harmonic generation of 1.064 μm incident light was measured on the thin films. The nonlinear optical susceptibility of the films was as high as 8.7 times that of quartz (∼3.0 pm/V), which is comparable to the bulk value. © 1995 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.55.-g Dielectric thin films

Si nanostructures fabricated by anodic oxidation with an atomic force microscope and etching with an electron cyclotron resonance source

E. S. Snow, W. H. Juan, S. W. Pang, and P. M. Campbell

Appl. Phys. Lett. 66, 1729 (1995); http://dx.doi.org/10.1063/1.113348 (3 pages) | Cited 39 times

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Nanometer‐scale Si structures have been fabricated by anodic oxidation with an atomic force microscope (AFM) and dry etching using an electron cyclotron resonance (ECR) source. The AFM is used to anodically oxidize a thin surface layer on a H‐passivated (100) Si surface. This oxide is used as a mask for etching in a Cl2 plasma generated by the ECR source. An etch selectivity ≳20 was obtained by adding 20% O2 to the Cl2 plasma. The AFM‐defined mask withstands a 70 nm deep etch, and linewidths∼10 nm have been obtained with a 30 nm etch depth. © 1995 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.65.-b Surface treatments

In situ x‐ray diffraction analysis of the C49–C54 titanium silicide phase transformation in narrow lines

R. A. Roy, L. A. Clevenger, C. Cabral, K. L. Saenger, S. Brauer, J. Jordan‐Sweet, J. Bucchignano, G. B. Stephenson, G. Morales, and K. F. Ludwig

Appl. Phys. Lett. 66, 1732 (1995); http://dx.doi.org/10.1063/1.113349 (3 pages) | Cited 42 times

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The transformation of titanium silicide from the C49 to the C54 structure was studied using x‐ray diffraction of samples containing arrays of narrow lines of preformed C49 TiSi2. Using a synchrotron x‐ray source, diffraction patterns were collected at 1.5–2 °C intervals during sample heating at rates of 3 or 20 °C/s to temperatures of 1000–1100 °C. The results show a monotonic increase in the C54 transition temperature by as much as 180 °C with a decreasing linewidth from 1.0 to 0.1 μm. Also observed is a monotonic increase in (040) preferred orientation of the C54 phase with decreasing linewidth. The results demonstrate the power of in situ x‐ray diffraction of narrow line arrays as a tool to study finite size effects in thin‐film reactions. © 1995 American Institute of Physics.
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61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
68.60.Dv Thermal stability; thermal effects
68.55.-a Thin film structure and morphology

Neutron powder diffraction at pressures beyond 25 GPa

S. Klotz, J. M. Besson, G. Hamel, R. J. Nelmes, J. S. Loveday, W. G. Marshall, and R. M. Wilson

Appl. Phys. Lett. 66, 1735 (1995); http://dx.doi.org/10.1063/1.113350 (3 pages) | Cited 32 times

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Full structural studies of condensed media under high pressure by neutron powder diffraction have been limited in practice to 2–3 GPa for several decades. This range is in general too small to allow a precise determination of the pressure dependence of atomic coordinates. As a consequence, almost no direct measurements exist, for example, of the pressure dependence of the bond lengths in H2 and the planetary ices. In this letter, a technique is presented which makes it possible to pressurize samples of 35 mm3 volume up to 30 GPa and to collect neutron diffraction patterns in a few hours by time‐of‐flight techniques. This method provides data which can be treated by Rietveld profile refinement methods, as demonstrated on a sample of D2O ice VII at 26 GPa. This represents a tenfold increase of the pressure range over which refinable neutron diffraction data can be obtained and should have a number of applications in such fields as fundamental physicochemistry, and geo‐ and planetary sciences. © 1995 American Institute of Physics.
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61.05.fm Neutron diffraction
62.50.-p High-pressure effects in solids and liquids
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics

SiO2 hole traps with small cross section

V. V. Afanas’ev, J. M. M. de Nijs, and P. Balk

Appl. Phys. Lett. 66, 1738 (1995); http://dx.doi.org/10.1063/1.113351 (3 pages) | Cited 15 times

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SiO2 hole traps with small cross section (σ≤10−15 cm2) in Al gated metal–oxide–silicon capacitors have been studied using vacuum ultraviolet hole injection in combination with capacitance voltage measurements. The data show that small σ hole traps are related to H/hole pairs or protons trapped in the oxide. Since accumulated positive charge and H vanish simultaneously from the oxide in times of the order of 102 s, it is proposed that they migrate together through the oxide as a proton. The small σ hole traps are not associated with defects in the as‐grown oxide; they are generated by radiation induced release of atomic H. Their number is governed by the rates of release and of removal (dimerization) of atomic H. © 1995 American Institute of Physics.
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73.61.Ng Insulators
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Growth of clean amorphous silicon–carbon alloy films by hot‐filament assisted chemical vapor deposition technique

A. S. Kumbhar, D. M. Bhusari, and S. T. Kshirsagar

Appl. Phys. Lett. 66, 1741 (1995); http://dx.doi.org/10.1063/1.113352 (3 pages) | Cited 7 times

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Amorphous silicon–carbon (a‐SiC) alloy films were deposited by using the hot‐filament chemical vapor deposition technique. The gas mixture containing different concentrations of silane in methane with additional dilution in hydrogen formed the source gas. Films were characterized for infrared and optical absorption and Raman scattering. The films deposited under ‘‘starving’’ hot‐filament conditions exhibited properties characteristic of stoichiometric carbon‐free a‐SiC material. © 1995 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Microstructure, thermal, and mechanical properties of nanostructured Cu‐9.5Ni‐4.0Sn‐7.5P

J. Li and T. M. Wang

Appl. Phys. Lett. 66, 1744 (1995); http://dx.doi.org/10.1063/1.113353 (3 pages) | Cited 1 time

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Nanostructured Cu‐9.5Ni‐4.0Sn‐7.5P samples represent a polycrystal microstructure of nanometer‐sized α‐Cu and Cu3P crystallites for crystallite sizes less than 20 nm and of nanometer‐sized α‐Cu, Cu3P, and Ni2P crystallites for crystallite sizes greater than 20 nm. The specific heat values between 300 K and 400 K for the nanostructured sample with crystallite size of 10 nm are about 20% higher than for the amorphous sample and about 40% higher than for the coarse‐grained sample. The hardness of the nanostructured sample with crystallite size of 10 nm is 30% higher than that of the amorphous sample and 110% higher than that of the coarse‐grained sample. The variation in hardness with the crystallite size for the nanostructured samples follows the Hall‐Petch relationship. © 1995 American Institute of Physics.
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62.20.-x Mechanical properties of solids
65.20.-w Thermal properties of liquids
65.40.gd Entropy
81.05.Rm Porous materials; granular materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Regular artificial nanometer‐scale structures fabricated with scanning tunneling microscope

Q. J. Gu, N. Liu, W. B. Zhao, Z. L. Ma, Z. Q. Xue, and S. J. Pang

Appl. Phys. Lett. 66, 1747 (1995); http://dx.doi.org/10.1063/1.113354 (3 pages) | Cited 10 times

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The scanning tunneling microscope (STM) has been used to fabricate grooves a few nm wide at room temperature by extracting atoms one by one from the Si(111)7×7 surfaces. When the direction of modification is parallel to the basic vector of Si(111)7×7 surfaces, grooves formed by such a process have atomically straight edges and lateral features as small as one 7×7 unit cell wide. The critical current under various voltages for fabricating grooves is measured. The modification mechanism is discussed based on the experiment data in this letter. © 1995 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)

Solid state ionic polishing of diamond

J. E. Yehoda and J. J. Cuomo

Appl. Phys. Lett. 66, 1750 (1995); http://dx.doi.org/10.1063/1.113355 (3 pages) | Cited 1 time

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A new process for polishing diamond is presented. The reaction and polishing take place at the interface of an oxygen superionic conductor (yittria‐stabilized zirconia) and the diamond. Oxygen anions are transported to the interface under the influence of an electric field and react with the diamond. It is believed that a volatile product of CO and/or CO2 is formed during the polishing. The process takes place at moderately low temperatures, without mechanical motion, and can be accomplished in ambient air, making it an attractive and useful method. In addition, the process is damage‐free with no polishing residue, as has been determined by energy dispersive x‐ray analysis. © 1995 American Institute of Physics.
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81.65.-b Surface treatments

Study of surface alignment of nematic liquid crystals on polyimide Langmuir–Blodgett films

Ruipeng Sun, Jianxin Guo, Ximin Huang, and Kai Ma

Appl. Phys. Lett. 66, 1753 (1995); http://dx.doi.org/10.1063/1.113356 (2 pages) | Cited 1 time

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The orientation effect of liquid crystal and polyimide molecules on the Langmuir–Blodgett (LB) films was studied. The orientation degree of polyimide chain in the LB films is less than that in the strong rubbing films. This result may be due to bad linear structure of polyimide. The 9 or 11 LB film layers may well align liquid crystals, but the orientation effect of liquid crystals on the polyimide LB films is worse than that on the strong rubbing films. The surface azimuthal anchoring energy of liquid crystals on the polyimide LB films was measured by a torque balance method proposed by our group. The intermolecular interaction between liquid crystal and polymer molecules is considered to be very important for aligning liquid crystals on the polymer surface. © 1995 American Institute of Physics.    
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Near‐surface electronic structure in GaAs (100) modified with self‐assembled monolayers of octadecylthiol

J. F. Dorsten, J. E. Maslar, and P. W. Bohn

Appl. Phys. Lett. 66, 1755 (1995); http://dx.doi.org/10.1063/1.113357 (3 pages) | Cited 22 times

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Passivation of the GaAs (100) surface by self‐assembled monolayers of octadecylthiol (ODT) has been studied using inelastic light scattering as a probe of the near‐surface electronic structure. Application of the ODT self‐assembled monolayers reduces the width of the depletion region at the surface of GaAs resulting in a reduction of the surface band bending, and the electron scattering time is increased as well. The ODT passivated surfaces are more stable to environmental degradation, over time and under temperature stress, than inorganic sulfide treated surfaces which have been reported. Organic thiol passivation may provide an attractive alternative to inorganic sulfide protocols for reduction of surface recombination velocities in III–V devices. © 1995 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena

Photoinduced electron paramagnetic resonance of the phosphorus vacancy in ZnGeP2

N. C. Giles, L. E. Halliburton, P. G. Schunemann, and T. M. Pollak

Appl. Phys. Lett. 66, 1758 (1995); http://dx.doi.org/10.1063/1.113358 (3 pages) | Cited 29 times

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The electron paramagnetic resonance (EPR) spectrum of the neutral phosphorus vacancy has been observed in as‐grown ZnGeP2 during illumination at liquid‐helium temperatures. Without illumination, this donor is a nonparamagnetic singly ionized phosphorus vacancy (VP+ center). Either above‐band‐gap light (514.5 nm) or below‐band‐gap light (632.8 nm) can produce the paramagnetic neutral state (VP0 center) of the donor. Principal values of the g matrix for the neutral donor are 1.944, 2.046, and 2.223. The angular dependence of the EPR spectrum suggests that the unpaired spin is unequally shared by two of the zinc ions neighboring the phosphorus vacancy. These phosphorus vacancies are the dominant donor in this highly compensated material, while the previously reported zinc vacancies are the dominant acceptor. © 1995 American Institute of Physics.
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71.55.Ht Other nonmetals
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.J- Point defects and defect clusters

High temperature electron cyclotron resonance etching of GaN, InN, and AlN

R. J. Shul, S. P. Kilcoyne, M. Hagerott Crawford, J. E. Parmeter, C. B. Vartuli, C. R. Abernathy, and S. J. Pearton

Appl. Phys. Lett. 66, 1761 (1995); http://dx.doi.org/10.1063/1.113359 (3 pages) | Cited 62 times

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Electron cyclotron resonance etch rates for GaN, InN, and AlN are reported as a function of temperature for Cl2/H2/CH4/Ar and Cl2/H2/Ar plasmas. Using Cl2/H2/CH4/Ar plasma chemistry, GaN etch rates remain relatively constant from 30 to 125 °C and then increase to a maximum of 2340 Å/min at 170 °C. The InN etch rate decreases monotonically from 30 to 150 °C and then rapidly increases to a maximum of 2300 Å/min at 170 °C. This is the highest etch rate reported for this material. The AlN etch rate decreases throughout the temperature range studied with a maximum of 960 Å/min at 30 °C. When CH4 is removed from the plasma chemistry, the GaN and InN etch rates are slightly lower, with less dramatic changes with temperature. The surface composition of the III–V nitrides remains unchanged after exposure to the Cl2/H2/CH4/Ar plasma over the temperatures studied. © 1995 American Institute of Physics.
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81.65.-b Surface treatments

Gain properties of doped GaAs/AlGaAs multiple quantum well avalanche photodiode structures

H. M. Menkara, B. K. Wagner, and C. J. Summers

Appl. Phys. Lett. 66, 1764 (1995); http://dx.doi.org/10.1063/1.113360 (3 pages) | Cited 3 times

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A comprehensive characterization has been made of the static and dynamical response of conventional and multiple quantum well (MQW) avalanche photodiodes (APDs). Comparison of the gain characteristics at low voltages between the MQW and conventional APDs show a direct experimental confirmation of a structure‐induced carrier multiplication due to interband impact ionization. Similar studies of the bias dependence of the excess noise characteristics show that the low‐voltage gain is primarily due to electron ionization in the MQW‐APDs, and to both electron and hole ionization in the conventional APDs. For the doped MQW APDs, the average gain per stage was calculated by comparing gain data with carrier profile measurements, and was found to vary from 1.03 at low bias to 1.09 near avalanche breakdown. © 1995 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Fq High-field and nonlinear effects

Electron and hole energy levels in InAs self‐assembled quantum dots

G. Medeiros‐Ribeiro, D. Leonard, and P. M. Petroff

Appl. Phys. Lett. 66, 1767 (1995); http://dx.doi.org/10.1063/1.113361 (3 pages) | Cited 111 times

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Capacitance spectroscopy is used to determine the allowed energy levels for electrons and holes in InAs self‐assembled quantum dots embedded in GaAs. Using this technique, the relative energy of the electron and hole states is measured with respect to their respective energy band minima in the GaAs. This allows the construction of an energy level diagram for these quantum dots which correlates well with previously observed photoluminescence data. By tuning the device geometry, a fine structure in the electron ground state is revealed and attributed to Coulomb charging effects. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Epitaxial all‐perovskite ferroelectric field effect transistor with a memory retention

Yukio Watanabe

Appl. Phys. Lett. 66, 1770 (1995); http://dx.doi.org/10.1063/1.113362 (3 pages) | Cited 73 times

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All‐perovskite ferroelectric field effect transistors (FET) are proposed, and switching behaviors of the prototype devices having a (Pb,La)(Zr,Ti)O3 as a gate insulator and a La1.99Sr0.01CuO4 as a channel layer were demonstrated. Marked improvements in device performances were obtained as compared with the previous ferroelectric FETs. Namely, the present device was written and erased at an operating voltage of 7 V with a pulse width of less than 1 ms, yielding resistance modulation up to about 10% and retaining its memory for more than 10 days at room temperature. Examinations show that the switching speed was limited by a delay constant and can therefore be improved up to 1 μs, and that the memory retention may not be limited by an intrinsic ferroelectric instability as previously suggested. © 1995 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Zn and Te desorption from the (100) ZnTe surface

S. Tatarenko, B. Daudin, and D. Brun‐Le Cunff

Appl. Phys. Lett. 66, 1773 (1995); http://dx.doi.org/10.1063/1.113363 (3 pages) | Cited 6 times

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The Zn and Te desorption times from the (100) ZnTe surface have been studied as a function of temperature using reflection high‐energy electron diffraction. For Zn desorption an activation energy of 1.8±0.1 eV is found. For Te, due to the existence of different bound states related to different surface reconstructions, c(2×2) and (2×1), activation energies of 1.7±0.1 and 2.50±0.05 eV have been measured. © 1995 American Institute of Physics.
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68.35.Md Surface thermodynamics, surface energies
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Evidence for ballistic transport of two‐dimensional electron gas at liquid‐nitrogen temperatures in a silicon metal–oxide semiconductor field effect transistor with a neck in the middle

Kan Takeuchi, Dai Hisamoto, and Hisaomi Yamashita

Appl. Phys. Lett. 66, 1776 (1995); http://dx.doi.org/10.1063/1.113364 (3 pages) | Cited 1 time

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The transconductance of a silicon metal–oxide semiconductor field effect transistor with a neck in the middle was measured at liquid‐nitrogen temperatures. The narrowest part of the gate with p+ isolations is 0.24 μm wide and about 0.2 μm long. The transconductance shows a peaked structure near the threshold voltage. The calculated transconductance based on the ballistic transport model of two‐dimensional electron gas explains well the peaked structure. © 1995 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.30.Tv Field effect devices

Enhanced real‐space electron transfer in charge injection transistors with source‐channel heterojunctions formed by graded AlxGa1−xAs layer and shallow Pd/Ge ohmic contacts

Jiun‐Tsuen Lai and Joseph Ya‐min Lee

Appl. Phys. Lett. 66, 1779 (1995); http://dx.doi.org/10.1063/1.113365 (3 pages) | Cited 1 time

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Charge injection transistors (CHINTs) with source‐channel heterojunctions are fabricated by using graded AlxGa1−xAs layers and shallow Pd/Ge ohmic contacts. Enhanced real‐space electron transfer is observed in CHINTs with source‐channel heterojunctions. The devices with graded AlxGa1−xAs launcher layers show lower threshold drain voltage for electron transfer, higher transconductance, and lower onset drain voltage for negative differential resistance than those without graded launchers. This is the first time that CHINT devices with source‐channel heterojunctions are demonstrated experimentally to have enhanced electron transfer. © 1995 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Photovoltaic investigations of interband transitions in SiGe/Si multiple quantum wells

Jianbao Wang, Dawei Gong, Fang Lu, Henghui Sun, and Xun Wang

Appl. Phys. Lett. 66, 1782 (1995); http://dx.doi.org/10.1063/1.113320 (3 pages) | Cited 2 times

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Photovoltaic effect measurements have been carried out for the strained Si1−xGex/Si multiple quantum well samples. The absorption structures of the transitions from heavy‐hole ground state (HH0) to the unconfined conduction (EC) states, light‐hole ground state to EC states as well as the transitions of phonon (transverse acoustic and transverse optical)‐assisted HH0‐EC excitons of the sample with x=0.25 are identified by the photovoltaic measurement at the temperature of 18 K. The agreement between the experimental results and the calculations based on simple theoretical models is fairly good. Due to the rapid increase of the background absorption, the structures of the transitions from excited hole subbands to the conduction states are very difficult to identify. For the sample with x=0.5, the absorption related to the defects originated from the partial relaxation of the large misfit strain between Si0.5Ge0.5 and Si gives a great influence upon the identification of the interband absorption structures of the multiple quantum well. © 1995 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
78.66.Li Other semiconductors

Determination of the conduction‐band discontinuities of In0.5Ga0.5P/In1−xGaxAs1−yPy by capacitance–voltage analysis

Yong‐Hoon Cho, Kwan‐Shik Kim, Sang‐Wan Ryu, Sang‐Ku Kim, Byung‐Doo Choe, and H. Lim

Appl. Phys. Lett. 66, 1785 (1995); http://dx.doi.org/10.1063/1.113321 (3 pages) | Cited 9 times

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The conduction‐band discontinuity ΔEc and interface charge density σ have been studied for In0.5Ga0.5P/In1−xGaxAs1−yPy (y<0.3) heterojunctions prepared by liquid phase epitaxy. The carrier concentration profiles of both normal (In0.5Ga0.5P on In1−xGaxAs1−yPy) and inverted (In1−xGaxAs1−yPy on In0.5Ga0.5P) structures are obtained by capacitance–voltage measurements, which agree well with the results of the self‐consistent numerical calculations. The current–voltage and deep‐level transient spectroscopy measurements confirm the validity of the result. It is found that ΔEc corresponds to 18% of the band‐gap difference ΔEg, for both normal and inverted structures. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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