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A five-element quarterwave-shifted distributed feedback laser array was designed and fabricated, and its performance reported.

Presents information on a study which described the long wavelength photoluminescence of InAs[sub1-x]Sb[subx] thin films that have been grown by molecular-beam epitaxy on gallium arsenide substrates. Optical properties of the films; Effect of lattice mismatch on the optical properties of the materials; Conclusions.

Examines pressure-induced resonance Raman Scattering (RRS) in strained quantum well structures. Details of experimental techniques used; Factor which causes RRS in quantum wells; Features of pressure-induced second-order phonon intensities in quantum wells.

Provides information on a study which estimated anticipated band alignments for pseudomorphic indium compound heterostructures. Methods; Results; Discussion.

Analyzes the equilibrium in-plane lattice parameter for lattice mismatched multilayers in an effort to obtain the expression for the misfit between multilayers. Computational formula for misfit expression; Equivalence between coherently strained multilayers and single strained layer; Implications of misfit dislocation densities.

Stimulated emission, obtainable at high optical pumping levels, has been used to follow the pressure dependence of the Γ-band gap of molecular beam epitaxial In0.53Ga0.47As on (001)InP. Hydrostatic pressure was generated using a diamond anvil cell, and all measurements were made at room temperature. The gap varies sublinearly with pressure for P>=10 kbar, having an initial slope of 12.44 meV/kbar. The deviation from a linear behavior is largely due to nonlinearities in the equation of state at higher pressures. The deformation potential (Ξd+ (1)/(3) Ξu-a) =-(7.79±0.4)eV, for the Γ-band gap. [ABSTRACT FROM AUTHOR]

InAs1-xSbx films have been successfully prepared by molecular beam epitaxy on (100) InAs substrates. Long-wavelength photoluminescence has been investigated over the complete compositional range. Luminescence peak wavelengths as long as 8 μm have been obtained for the first time among III-V compound semiconductor materials in spite of the existence of a large lattice mismatch. These results are indicative of high-quality material. [ABSTRACT FROM AUTHOR]

The effects of lattice mismatch induced coherency strain on the direct (Γ) band gap of InxGa1-xAs alloys for commensurate growth on (001) InP substrates are presented. It is found that the low-temperature (T≊2 K) band gap of the strained ternary varies between 1.0 and 0.48 eV for 0≤x≤1.0. The band-gap difference ΔEg between the strained ternary and cubic InP varies therefore between 0.42 and 0.94 eV. The partitioning of ΔEg between conduction and valence bands has yet to be determined for nonlattice-matched compositions (i.e., x≠0.53). In view of the large calculated variation in ΔEg it is anticipated that coherency strain may provide a means for tailoring band discontinuities in this technologically important materials system. Potential applications are briefly reviewed. [ABSTRACT FROM AUTHOR]

Rapid thermal annealing (RTA) has been found to significantly improve the crystalline quality of epitaxial GaAs grown on Si (100) substrates. After RTA at 900 °C for 10 s, the percentage of displaced atoms near the GaAs/Si interface, as estimated by Rutherford backscattering/channeling, decreased from 20 to 7%. Photoluminescence intensity (PL) after RTA increased significantly (as much as sixfold in some cases), with the actual increase varying from sample to sample and with annealing conditions. In some cases, the PL intensity after RTA was comparable to the PL intensity obtained from GaAs grown on GaAs substrate under similar conditions. Rapid thermal annealing at 940 °C resulted in a degradation of the PL intensity as compared to annealing at 900 °C. Also, the PL peaks after RTA were found to shift to lower energies by 2–5 meV at low temperatures. [ABSTRACT FROM AUTHOR]

We have used the hot-carrier Shubnikov–de Haas effect to measure the power loss by hot two-dimensional holes in coherently strained Ge0.2Si0.8/Si heterostructures. The measured power loss versus carrier temperature data are best described by the two-dimensional formalism of P. J. Price [J. Appl. Phys. 53, 6864 (1982)] assuming weak screening. Excellent agreement with experiment is obtained only if scattering of the acoustic mode phonons by both the deformation potential and the piezoelectric coupling mechanisms are considered. We are therefore able to deduce a value for the piezoelectric constant for Ge0.2Si0.8 which is approximately 35% of that for InAs (e2pz≊0.22×108 dyne/cm2). In light of the fact that charge transfer effects are expected to be small in bulk (unstrained) GexSi1-x, the present observations are indicative of either a large strain induced change in ionicity or of scattering of acoustic phonons from ordered domains via the piezoelectric mechanism. [ABSTRACT FROM AUTHOR]

The self-consistent ab initio pseudopotential results of C. G. Van de Walle and R. M. Martin [J. Vac. Sci. Technol. B 3, 1256 (1985)] have been combined with a phenomenological deformation potential theory to estimate the band gap and band offsets for coherently strained multilayers of GexSi1-x/Si for growth on <001> GeySi1-y substrates. It is found that ΔEc is negligible and the narrower GexSi1-x gap falls within the wider Si gap (type I band alignment) if the Si in the multilayers is cubic, whereas ΔEc can be appreciable and the GexSi1-x conduction-band edge tends to be higher in energy than the Si conduction-band edge(type II band alignment) if both the Si and the GexSi1-x are strained. In particular, the present results resolve the seeming paradox which arose from interpretations of modulation doping experiments using heterojunctions grown either on Si<001> substrates or on an unstrained alloy buffer layer. [ABSTRACT FROM AUTHOR]

We have used photocurrent spectroscopy to measure the optical absorption spectra of coherently strained layers of Ge[sub x]Si[sub 1 - x] grown on 〈001〉 Si by molecular beam epitaxy. A dramatic lowering of the indirect band gap, relative to that of unstrained bulk Ge-Si alloys, is observed. Our results for 0≤x≤0.7 are in remarkably good agreement with recent calculations of the effects of misfit strain on the band edges of coherently strained Ge-Si heterostructures. At x = 0.6, the gap is lower than that of pure Ge. [ABSTRACT FROM AUTHOR]

A calculation of the critical layer thickness h[sub c] for growth of Ge[sub x] Si[sub 1-x] strained layers on Si substrates is presented for 0≤x≤1.0. The present results are obtained assuming misfit dislocation generation is determined solely by energy balance. This approach differs therefore from previous theories (e.g., Matthews et al.), in which the absence of mechanical equilibrium for grown-in threading dislocations determines the onset of the generation of interracial misfit dislocations. It is assumed that interracial misfit dislocations will be generated when the areal strain energy density of the film exceeds the energy density associated with the formation of a screw dislocation at a distance from the free surface equal to the film thickness h. For films thicker than this critical value, screw (and edge) dislocations will be generated at the film/substrate interface. Values obtained for the critical thickness versus lattice mismatch are in excellent agreement with measurements of he for Ge[sub x]Si[sub 1-x] strained layers on Si substrates. [ABSTRACT FROM AUTHOR]

We report the first observation of the modulation doping effect in Si/Ge0.2Si0.8 heterojunctions grown by molecular beam epitaxy. Peak hole mobilities of ∼3300 cm2 V-1 s-1 have been observed at 4.2 K. These values, although nonoptimum, are comparable to the best reported values for holes in Si/SiO2 inversion layers. Low temperature, angular dependent, Shubnikov-de Haas measurements have demonstrated the two-dimensional nature of the hole gas and yield a surface carrier density of 3.5×1011 cm-2. From the temperature dependence of the Shubnikov-de Haas amplitudes a hole effective mass of 0.30±0.02mo has been derived. Identical measurements on n-type heterojunctions having the same Ge content (x=0.2) have failed to show a sustained enhancement of mobility at low temperatures, indicating that ΔEv>ΔEc. [ABSTRACT FROM AUTHOR]

Examines the performance characteristics of the pseudomorphic Ge[sub x]Si[sub 1-x]/silicon (Si) strained-layer quantum well infrared (IR) photodetector on (001) Si. Range of IR photodetector operation; Factors attributed to the broadband photoresponse of the device; Quantum efficiency of the Fourier transform infrared measurement.

We report a new photoluminescence defect spectrum with a no-phonon transition at 1.0192 eV which emerges in many silicon layers grown on silicon substrates by molecular beam epitaxy. Comparison of the no-phonon transition and the chief local mode (hω=7.5 meV) to the well-established Cu-related spectrum at 1.0145 eV suggests that the new defect incorporates Cu as well. Deep level transient measurements support the presence of Cu in the epilayers. We suggest that this defect spectrum has recently been observed by others but was not identified and associated with Cu. [ABSTRACT FROM AUTHOR]