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20 Mar 1995

Volume 66, Issue 12, pp. 1443-1566

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Large and stable second harmonic generation in a crystalline phase of a ferroelectric liquid crystal

S. Sprunt, J. Naciri, B. R. Ratna, R. Shashidhar, B. Bihari, J. Kumar, and S. K. Tripathy

Appl. Phys. Lett. 66, 1443 (1995); http://dx.doi.org/10.1063/1.113648 (3 pages) | Cited 8 times

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Second harmonic generation (SHG) has been studied in a nitro‐substituted ferroelectric liquid crystal cooled from the smectic‐C∗ into a three‐dimensional crystalline (K) phase in an applied electric field. The SHG efficiency in the K phase is found to be deff≳4.5 pm/V, about 25 times the value in the SmC∗ phase, and, unlike the SmC∗ case, remains constant in zero field for ≳25 h. A quantitative analysis of the polarization dependence of the SHG reveals that the dominant d coefficients contributing to the measured signal differ for the two phases, and that the orientation of the liquid‐crystal director in the K phase is modulated in one dimension. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Df Liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Picosecond multiwavelength optical parametric generation in lithium triborate

Xiang Liu, Zuyan Xu, Baichang Wu, and Chaungtian Chen

Appl. Phys. Lett. 66, 1446 (1995); http://dx.doi.org/10.1063/1.113649 (3 pages) | Cited 3 times

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The retracing behavior of the phase‐matching angle (RBPA) in optical parametric generation (OPG) based on a LiB3O5 (LBO) crystal and pumped at 532 nm by a frequency doubled, passive‐active mode‐locked Nd:YAG laser is investigated. Two pairs of radiations, which are simultaneously generated in the OPG, are observed and the spectral radiant power of the four tunable beams are obtained, showing good agreement with the theoretical calculation results. Together with the parametric process, two kinds of frequency‐mixing waves are produced and this novel multiwavelength interaction phenomenon is analyzed. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

LiNbO3 optical waveguides by Zn diffusion from vapor phase

B. Herreros and G. Lifante

Appl. Phys. Lett. 66, 1449 (1995); http://dx.doi.org/10.1063/1.113650 (3 pages) | Cited 11 times

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Fabrication of optical waveguides on LiNbO3 by Zn diffusion from the vapor phase has been demonstrated, using a specially designed diffusion apparatus. The planar waveguides on z‐cut samples support both TE and TM propagations, indicating an increase of refractive indices for n0 and ne. Energy dispersive x‐ray analysis measurements confirm the diffusion of Zn into the crystal, and analysis of the content of Zn as a function of diffusion depth for samples treated at different temperatures indicates much higher diffusion coefficients than those obtained for Ti diffusion in LiNbO3. The technique is versatile, easy to operate, and allows fabrication of waveguides at temperatures as low as 600–700 °C, thus preventing Li outdiffusion. © 1995 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
66.30.J- Diffusion of impurities

Correlation between optical properties, composition, and deposition parameters in pulsed laser deposited LiNbO3 films

C. N. Afonso, J. Gonzalo, F. Vega, E. Dieguez, J. C. Cheang Wong, C. Ortega, J. Siejka, and G. Amsel

Appl. Phys. Lett. 66, 1452 (1995); http://dx.doi.org/10.1063/1.113651 (3 pages) | Cited 10 times

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The correlation between the optical properties and composition of lithium niobate films is investigated in films deposited by laser ablation of single‐crystal LiNbO3 and Li enriched LiNbO3 sintered targets under different oxygen pressures and laser fluences. The results show that the variation of the film refractive index is in many cases related to the deposition process itself, rather than to a variation of the film composition. The experimental conditions to produce stoichiometric films with optical properties similar to those of the bulk material are discussed. © 1995 American Institute of Physics.  
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81.15.Fg Pulsed laser ablation deposition
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.55.-g Dielectric thin films

Spectral and spatial resolution of photopumped II–VI single quantum well lasers

D. M. Bagnall, A. Ralston, K. P. O’Donnell, P. C. Smith, P. Wright, and B. Cockayne

Appl. Phys. Lett. 66, 1455 (1995); http://dx.doi.org/10.1063/1.113652 (3 pages) | Cited 2 times

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Simple II–VI laser cavities were formed by cleaving epitaxial ZnSe samples containing a single CdSe quantum well of mean thickness about 1 monolayer. Time‐integrated stimulated emission spectra of these lasers show little evidence of mode structure. A video camera enables temporal resolution of the stimulated emission spectra. Mode structure appears on the time‐resolved spectra. In addition, however, video spectroscopy reveals spatial variations of wavelength and intensity in the laser output which are not well understood. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.47.-p Spectroscopy of solid state dynamics
78.45.+h Stimulated emission
78.66.Hf II-VI semiconductors

Analytical solution of wave mixing between short optical pulses in a semiconductor optical amplifier

M. Shtaif and G. Eisenstein

Appl. Phys. Lett. 66, 1458 (1995); http://dx.doi.org/10.1063/1.113653 (3 pages) | Cited 33 times

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An analytical solution to the problem of nondegenerate four wave mixing in a semiconductor optical amplifier emphasizing operation with short optical pulses is described. Calculated conversion efficiencies for pulses are significantly larger than for cw fields and are pulse width dependent. Conditions for optimum conversion efficiencies in terms of the pump input energy and the relative temporal alignment between the pulses are presented. © 1995 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.47.-p Spectroscopy of solid state dynamics

Improved structures for evanescent wave sensors

F. Rehouma, W. Elflein, D. Persegol, A. Kevorkian, G. Clauss, P. Benech, and R. Rimet

Appl. Phys. Lett. 66, 1461 (1995); http://dx.doi.org/10.1063/1.113654 (2 pages) | Cited 3 times

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Integrated optics evanescent wave sensors suffer from attenuation losses and reduced contrast ratio when the sensing layer index is too close to the waveguide index. This is attributed to an increase in mode mismatch at inner interfaces of the devices. By properly balancing the losses on each arm of an integrated Mach–Zehnder the contrast ratio is increased to nearly 100% on the entire index range, furthermore, a new technique used to make a smooth transition between sensing and nonsensing waveguides reduced the losses by 5 dB. © 1995 American Institute of Physics.
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42.79.Pw Imaging detectors and sensors
42.79.Gn Optical waveguides and couplers

Pulsed ultraviolet laser deposition of SiO2 films at 248 nm

Paul B. Comita, Janos Farkas, B. Yang, Y. H. Chuang, J. O’Connor, K. C. Liu, and M. G. Cohen

Appl. Phys. Lett. 66, 1463 (1995); http://dx.doi.org/10.1063/1.113655 (3 pages) | Cited 4 times

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Photochemical laser‐induced deposition of silicon dioxide thin films is reported with excimer laser radiation at 248 nm. A deposition rate of 0.25 A/pulse was obtained at room temperature. The deposited films were characterized by scanning electron microscopy, x‐ray photoelectron spectroscopy, ellipsometry and optical microscopy. The films exhibited excellent properties (n=1.47, k=0.05) derived from ellipsometry data. The deposition required no oxidizing coreactant. © 1995 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition

Acousto‐optic technique: A new nondestructive technique to evaluate thin layered structures

M. Wevers, S. Devolder, P. De Meester, and O. Leroy

Appl. Phys. Lett. 66, 1466 (1995); http://dx.doi.org/10.1063/1.113656 (3 pages) | Cited 7 times

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On laboratory scale a new nondestructive technique has been elaborated for the quality control of layered structures. This technique is called the ‘‘acousto‐optic technique’’ and it measures the modulation of ultrasound reflected by a layered material optically in amplitude and phase using laser beams crossing the ultrasonic beams (incident and reflected). The most important characteristics of layered structures which have been investigated are the thickness and the thickness variations within a layer and the presence of artificial defects. Only when the ultrasound is incident in the Rayleigh angle of the substrate material, the phase differences measured obtain important information on the quality of the layered structure. The experimental results underline the results already obtained from the theoretical models elaborated for this technique. © 1995 American Institute of Physics.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology

Dual‐laser ablation for particulate‐free film growth

S. Witanachchi, K. Ahmed, P. Sakthivel, and P. Mukherjee

Appl. Phys. Lett. 66, 1469 (1995); http://dx.doi.org/10.1063/1.113657 (3 pages) | Cited 24 times

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A novel dual laser ablation process that leads to particulate‐free film growth is presented. A pulsed CO2 laser and an excimer (KrF) laser have been spatially overlapped on a Y2O3 target with a temporal delay between the pulses. The particulate density of the films grown by this method are at least three orders of magnitude smaller than the particulate density of a single excimer laser ablated film of similar thickness. In addition, a time‐of‐flight ion probe study indicates a sixfold enhancement of the plume species kinetic energies under dual‐laser ablation. The degree of the plume excitation is observed to depend strongly on the delay between the laser pulses. © 1995 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Surface topography and step orientation during metalorganic vapor phase epitaxy of InP

J. E. Epler, H. P. Schweizer, J. Pedersen, and J. Söchtig

Appl. Phys. Lett. 66, 1472 (1995); http://dx.doi.org/10.1063/1.113658 (3 pages) | Cited 7 times

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The surface topography during initial and steady state epitaxial growth of InP on InP is monitored with in situ diffuse elastic light scattering. The in situ results are compared with the end‐of‐run topography measured by ex situ atomic force microscopy. Upon growth initiation, an increase in surface roughness is observed with steps oriented perpendicular to the [011] and [010] direction. After several nanometers of InP deposition, the surface topography planarizes and steady state step‐flow epitaxy develops with steps aligned to the pregrowth terrace. © 1995 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Current density dependence of electromigration failure of submicron width, multilayer Al alloy conductors

A. S. Oates

Appl. Phys. Lett. 66, 1475 (1995); http://dx.doi.org/10.1063/1.113659 (3 pages) | Cited 15 times

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Electromigration failure of Al alloy metallization systems is one of the main concerns for integrated circuit reliability as feature sizes are reduced into the submicron regime. One of the most important aspects of electromigration failure is the current density dependence of the failure time. Many studies have been conducted for widths above 1 μm and the consensus of these studies indicates that a current density exponent, n=2, describes microstructure related failure of the metallization. There is very little data available, however, for feature sizes close to 0.5 μm, particularly for metallizations consisting of Al alloys clad by refractory layers. In this letter we investigate the current density dependence of microstructure related failure for narrow (0.6 μm) conductors with multilayer TiN refractory layers, and correlate this dependence with void formation by electromigration. We show that the current density dependence of microstructural failure in such narrow conductors differs significantly from that observed for widths above 1 μm. At 0.6 μm n as low as 1 is obtained compared with n=2 at 1.2 μm for microstructure‐related failure of long, multilayer stripes. The number of voids formed during accelerated testing and their average nucleation rate appear to be independent of the current density for 0.6 μm stripes, contrary to findings for wider stripes. It is suggested that growth of voids determines the failure kinetics of narrow stripes. © 1995 American Institute of Physics.
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66.30.Qa Electromigration
85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Transmission electron microscopic study of c ‐BN films deposited on a Si substrate

Syuichi Watanabe, Shojiro Miyake, Weilie Zhou, Yuichi Ikuhara, Tetsuya Suzuki, and Masao Murakawa

Appl. Phys. Lett. 66, 1478 (1995); http://dx.doi.org/10.1063/1.113660 (3 pages) | Cited 24 times

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Microstructure of c‐BN films synthesized by the ion‐plating method were observed and characterized by high resolution electron microscopy and microdiffraction. The c‐BN films of ∼0.2 μm thickness were deposited on top of ∼0.05 μm of h‐BN, which was oriented with its c‐axis parallel to the substrate. Lattice image taken along the 〈011〉 direction showed that c‐BN film was well crystallized with an interplanar distance ∼2.1 Å, although the grain size was extremely small, from 5 to 20 nm. Further, the microdiffraction pattern along the 〈011〉 direction by focusing the electron beam to ∼20 Å, clearly showed that the small grains consisted of a single crystal of c‐BN. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Effect of poling on piezoelectric properties of lead zirconate titanate thin films formed by sputtering

Shunji Watanabe, Takamitsu Fujiu, and Toru Fujii

Appl. Phys. Lett. 66, 1481 (1995); http://dx.doi.org/10.1063/1.113661 (3 pages) | Cited 32 times

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Lead zirconate titanate (PZT) thin film was formed on Pt/Ta/Si3N4/Si(100) substrate at 400 °C by sputtering and then annealed at 650 °C in air. The PZT film was 1 μm thick and had dielectric permittivity of 980, loss tangent of 0.05, remanent polarization of 31 μC/cm2, and coercive field of 110 kV/cm. Piezoelectric property of the film formed on silicon cantilever was estimated from the converse effect. Poling at 5 kV/mm increased the property by a factor of 1.2 to 3.4, resulting in converse piezoelectric constant (d31) varying from −84 to −102 pC/N. © 1995 American Institute of Physics.
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77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Cd Deposition by sputtering

Direct bonding of LiNbO3 single crystals for optical waveguides

Yoshihiro Tomita, Masato Sugimoto, and Kazuo Eda

Appl. Phys. Lett. 66, 1484 (1995); http://dx.doi.org/10.1063/1.113662 (2 pages) | Cited 18 times

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A new fabrication method of optical waveguides using direct bonding of lithium niobate single crystals without using any bonding agents has been developed. The bonded interface was found very uniform and the bonding was performed in an atomic scale in spite of a relatively low heat‐treatment temperature of 400 °C. It was confirmed to be possible to fabricate optical waveguides using the direct bonding. This method is very attractive to obtain high‐performance optical guided‐wave devices because of its versatility. © 1995 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Homoepitaxial diamond film deposition on a brilliant cut diamond anvil

Thomas S. McCauley and Yogesh K. Vohra

Appl. Phys. Lett. 66, 1486 (1995); http://dx.doi.org/10.1063/1.113663 (3 pages) | Cited 12 times

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A thick, homoepitaxial diamond film was deposited on the microcracked (100) tip of a brilliant cut type Ia natural diamond anvil by microwave plasma‐assisted chemical vapor deposition (MPCVD). The rapid (up to 20 μm/h), highly anisotropic growth resulted in a modification of the original geometry of the central flat and culet regions. The size of the diamond culet grew from 350 to ∼800 μm in diameter in about 8 h. The deposited film was characterized by optical microscopy, micro‐Raman and photoluminescence (PL) spectroscopy. Raman analysis of the deposit confirms that its crystalline quality is comparable to that of the substrate, and that it contains no amorphous or graphitic phases of carbon. The epitaxial overlayer exhibits two prominent PL bands not observed from the substrate with zero‐phonon (ZPL) lines at 1.945 and 2.156 eV, which are attributed to nitrogen‐related defect complexes. The present work shows the potential viability of high growth rate homoepitaxy by MPCVD for numerous industrial and scientific applications, such as high pressure research. © 1995 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Deposition of boron‐nitride films by nitrogen sputtering from a boron‐metal target

H. Jensen, U. M. Jensen, and G. Sorensen

Appl. Phys. Lett. 66, 1489 (1995); http://dx.doi.org/10.1063/1.113664 (3 pages) | Cited 7 times

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This contribution deals with reactive growth of boron‐nitride films by a rf nitrogen‐sputtering process from a boron‐metal target; thus nitrogen is functioning both as sputter and reactive gas. Only few and superficial reports of reactive sputter depositions from a metallic boron target in various argon/nitrogen mixtures exist, compared to the number of reports on rf sputtering from a BN target. Nitrogen sputtering of boron‐metal has previously not been reported. It was shown by Fourier‐transform infrared (FTIR) spectroscopy that the hexagonal structure of BN exclusively was deposited. Sputter rates were measured and showed no dependence on the reactive‐gas flow and only a marginal dependence on sputter‐gas mixtures containing 20% of krypton, argon, or helium. The reported nitrogen‐sputtering process appears to be appropriate for exploration of the key parameters for phase control in BN growth and for additional surface engineering processes such as substrate bias and post‐ion bombardment. © 1995 American Institute of Physics.
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81.15.Cd Deposition by sputtering

N depth profiles in thin SiO2 grown or processed in N2O: The role of atomic oxygen

E. C. Carr, K. A. Ellis, and R. A. Buhrman

Appl. Phys. Lett. 66, 1492 (1995); http://dx.doi.org/10.1063/1.113665 (3 pages) | Cited 68 times

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Atomic oxygen, which can be liberated as an intermediate product in the decomposition of N2, is shown to be effective in removing N previously incorporated in SiO2 layers grown in N2O. This removal results in a N distribution that is sharply peaked at the Si–SiO2 interface for oxides grown in N2O by rapid thermal oxidation, but in a flat N distribution for N2O oxides grown in a furnace where the concentration of atomic oxygen is generally not substantial at the wafer position. This effect provides a means of tuning N profiles in a manner that may be useful for optimizing oxide quality. © 1995 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.-b Surface treatments

Silicon doping of GaN using disilane

L. B. Rowland, K. Doverspike, and D. K. Gaskill

Appl. Phys. Lett. 66, 1495 (1995); http://dx.doi.org/10.1063/1.113666 (3 pages) | Cited 28 times

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The n‐type doping of GaN by organometallic vapor phase epitaxy using Si2H6 on sapphire has been demonstrated. The electron concentration depended linearly on Si2H6 to trimethylgallium mole fraction ratio. State‐of‐the‐art values of 300 K electron mobility were obtained for electron concentrations from 1×1017–4×1019/cm3 with no apparent increase in compensation at either the lowest or highest concentrations studied. Electron concentrations obtained using a given concentration of disilane were constant with growth temperature in the range 980–1040 °C. © 1995 American Institute of Physics.
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61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.50.Dn Low-field transport and mobility; piezoresistance

Efficient excitation transfer in silicon studied by Fourier transform photoluminescence excitation spectroscopy

Mandeep Singh, W. M. Chen, N. T. Son, and B. Monemar

Appl. Phys. Lett. 66, 1498 (1995); http://dx.doi.org/10.1063/1.113667 (3 pages) | Cited 1 time

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Direct experimental evidence of excitation transfer in the recombination via deep defects in silicon is provided, by a novel approach of Fourier transform photoluminescence excitation spectroscopy. The 735 meV iron‐related defect in Si is used as a model case. It is shown that this defect can be excited via two deep states of other centers that give rise to broad lines in the excitation spectrum at 976.3 and 1115.6 meV. The linewidths of these features infer extremely efficient transfer processes. Such an efficient excitation transfer is expected to play an important role in excitation and recombination processes in silicon. © 1995 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.55.Hx Other solid inorganic materials
71.55.Cn Elemental semiconductors

SiC power device passivation using porous SiC

C. I. Harris, A. O. Konstantinov, C. Hallin, and E. Janzén

Appl. Phys. Lett. 66, 1501 (1995); http://dx.doi.org/10.1063/1.113668 (2 pages) | Cited 9 times

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A novel technique for the passivation of high power SiC p‐n diodes using porous SiC is demonstrated. An increase from around 250 to 600 V in the reverse breakdown voltage is observed following the passivation treatment. The breakdown mode is also reversible in the passivated case in contrast to the permanent degradation in the nontreated device. © 1995 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b Surface treatments
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Use of InN for Ohmic contacts on GaAs/AlGaAs heterojunction bipolar transistors

F. Ren, C. R. Abernathy, S. N. G. Chu, J. R. Lothian, and S. J. Pearton

Appl. Phys. Lett. 66, 1503 (1995); http://dx.doi.org/10.1063/1.113669 (3 pages) | Cited 14 times

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Degenerately doped (n=5×1020 cm−3) InN grown by metalorganic molecular beam epitaxy is used for emitter Ohmic contacts on GaAs/AlGaAs heterojunction bipolar transistors (HBTs). Both abrupt InN/GaAs and graded GaAs/InGaAs/InN contact structures were investigated. Although, the contact resistivity of nonalloyed Ti/Pt/Au on InN was achieved as low as 1.8×10−7 Ω cm2, formation of a thin GaN layer at the interface of the InN/GaAs system limits nonalloyed TiPtAu metallization to contact resistivities of 10−4 Ω cm2. Whereas the graded structure, GaAs/InGaAs/InN material, system produces values of 5×10−7 Ω cm2 which resulted in the formation of conductive InN from nitridation of InAs instead of the GaN layer for the InN/GaAs system. The InN‐based emitter contacts have superior surface morphologies to the more conventional InAs layers. The C‐doped base (p=7×1019 cm−3) HBTs utilizing 2×5 μm2 InN‐based emitter contacts is demonstrated with dc gains of 35. © 1995 American Institute of Physics.
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85.30.Pq Bipolar transistors
73.40.Cg Contact resistance, contact potential

Flow rate modulation epitaxy of AlGaAs/GaAs quantum wires on nonplanar substrate

Xue‐Lun Wang, Mutsuo Ogura, and Hirofumi Matsuhata

Appl. Phys. Lett. 66, 1506 (1995); http://dx.doi.org/10.1063/1.113670 (3 pages) | Cited 49 times

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Flow rate modulation epitaxy (FME) is applied to the low‐temperature growth of AlGaAs/GaAs quantum wires (QWRs) on nonplanar substrates. The growth selectivity is found to be enhanced greatly by the use of FME, as compared with the conventional metalorganic chemical vapor deposition due to the enhanced migration of Ga species. An AlGaAs/GaAs QWR with a central thickness of about 9 nm and a lateral width of about 28 nm is grown at 600 °C on a V‐grooved substrate. Good photoluminescence properties are observed from the grown QWR, with the peak energy being in good agreement with the calculated energy level of a parabolic shape lateral confinement potential. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors

Selective growth of zinc‐blende, wurtzite, or a mixed phase of gallium nitride by molecular beam epitaxy

T. S. Cheng, L. C. Jenkins, S. E. Hooper, C. T. Foxon, J. W. Orton, and D. E. Lacklison

Appl. Phys. Lett. 66, 1509 (1995); http://dx.doi.org/10.1063/1.113671 (3 pages) | Cited 86 times

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We report on the growth of GaN with a zinc‐blende, wurtzite, or a mixed phase structure on (001)GaP and (001)GaAs substrates by a low‐temperature modified molecular beam epitaxy technique. By systematically varying the incident arsenic overpressure, films grown at a moderate substrate temperature of ≊620 °C show predominately wurtzite α‐GaN, zinc‐blende β‐GaN, or a mixed phase of the two. Films containing only the metastable phase β‐GaN were achieved by using a relatively high growth temperature of ≊700 °C and with an arsenic overpressure of ≊2.4×10−5 Torr. X‐ray diffraction measurements indicate an improved crystalline quality for the layers grown at ≊700 °C compared to those grown at ≊620 °C as evident by a narrower full width at half‐maximum of 35 min for β‐GaN, which is among the narrowest reported to date. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Absorption in p‐Si1−xGex quantum well detectors

D. J. Robbins, M. B. Stanaway, W. Y. Leong, R. T. Carline, and N. T. Gordon

Appl. Phys. Lett. 66, 1512 (1995); http://dx.doi.org/10.1063/1.113630 (3 pages) | Cited 12 times

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The normal incidence absorption between 2 and 14 μm in a pseudomorphic p‐Si0.81Ge0.19/Si multiple quantum well sample with doping 5×1012 cm−2 per well is described by a Drude conductivity characteristic of free carriers, with an in‐plane mobility of 32 cm2/V s and a relaxation time of 5.5 fs at 77 K. When the absorption is scaled with dopant concentration these parameters predict quantum efficiencies for quantum well infrared photodetectors in reasonable agreement with experiment.
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73.50.Pz Photoconduction and photovoltaic effects
85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Li Other semiconductors
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