Infrared photoluminescence (PL) from InSb, InAs, and InAs1−xSbx (x<0.3) epitaxial layers grown by atmospheric pressure organometallic vapor phase epitaxy has been investigated for the first time over an extended temperature range. The values of full width at half maximum of the PL peaks show that the epitaxial layer quality is comparable to that grown by molecular-beam epitaxy. The observed small peak shift with temperature for most InAs1−xSbx epilayers may be explained by wave-vector-nonconserving transitions involved in the PL emission. For comparison, PL spectra from InSb/InSb and InAs/InAs show that the wave-vector-conserving mechanism is responsible for the PL emission. The temperature dependence of the energy band gaps, Eg, in InSb and InAs is shown to follow Varshni’s equation Eg(T)=Eg0−αT2/ (T+β). The empirical constants are calculated to be Eg0=235 meV, α=0.270 meV/K, and β=106 K for InSb and Eg0=415 meV, α=0.276 meV/K, and β=83 K for InAs.
InAs1−xBix with x≤0.026 and InAs1−x−ySbyBix with x≤0.017 and y≤0.096 have been successfully grown on InAs (100) oriented substrates by atmospheric pressure organometallic vapor phase epitaxy using the precursors trimethylindium, trimethylbismuth, trimethylantimony, and arsine. Good surface morphologies for both InAsBi and InAsSbBi epitaxial layers were obtained at a growth temperature of 400 °C. A key growth parameter is the V/III ratio. Only a very narrow range near 4 (considering the incomplete pyrolysis of AsH3) yields smooth InAsBi epilayers. Typical growth rates were 0.02 μm/min. X-ray diffractometer scans show clearly resolved Kα1 and Kα2 peaks for the layer of InAs0.889Sb0.096Bi0.015 grown on an InAs substrate with a graded transition layer to accommodate the lattice parameter difference. The half widths of the peaks are comparable to those of the substrate. For the first time, photoluminescence (PL) at 10 K from these Bi-containing alloys has been measured. The PL peak energy is seen to decrease with increasing Bi concentration at a rate of 55 meV/at. % Bi. InAsSbBi is a potential material for infrared detectors operating in the wavelength range from 8 to 12 μm.
CuPt type ordering, which consists of a monolayer compositional modulation along one of the 4 〈111〉 directions in the lattice, was studied using transmission electron microscopy for GaAs1−xPx with values of x extending from 0.25 to 0.85. The samples were grown by organometallic vapor phase epitaxy on nominal (001) GaAs substrates that were misoriented by varying amounts in three directions. No CuPt type ordering was observed for GaAs1−xPx with x ≤0.35, while ordering was found to occur for 0.4≤x≤0.85. The direction of substrate misorientation has a major effect on the determination of which of the four possible CuPt variants are formed for 0.4≤x≤0.85. Two variants, with ordering on the (1̄11) and (11̄1) planes, appear for epilayers grown on substrates oriented exactly on the (001) plane and for substrates misoriented by 6° towards the [110] direction. Only one variant, with ordering on the (1̄11) plane, appears for epilayers grown on substrates misoriented by 6° towards [1̄10]. These ordering-induced spots observed in transmission electron diffraction (TED) patterns for GaAsP occur only for the [110] cross section. From TED studies of GaInP grown on similar substrates, we conclude that the CuPt variants in GaAsP are exactly the same as for GaInP. Further evidence supporting this conclusion was obtained by growing first a layer of GaInP followed by a layer of GaAsP. High-resolution dark field electron micrographs show domains of the same variants in both layers. A mechanism describing the formation of the specific ordered variant for both GaAsP and GaInP is proposed. From studies of ordering in a strain-layer superlattice, the strain due to lattice mismatch was found to play no significant role in the propagation of ordered domains. Microtwins, also generated due to lattice mismatch, can act as domain boundaries and prevent the propagation of the ordered domains.
An unexpected self-organized superlattice structure has been observed in the AlGaInAsSb pentanary alloys grown by metalorganic vapor-phase epitaxy. The samples were studied by transmission electron microscopy, double-crystal x-ray diffraction, and secondary ion mass spectrometry measurements. The modulation strength and period of the self-organized superlattice are correlated to the alloy composition.
The quaternary semiconductor alloy GaxIn1−xAsySb1−y has been investigated using Raman scattering spectroscopy in the spectral region from 150 to 300 cm−1 at room temperature. The Raman spectra exhibit two- or three-mode behavior depending on the composition. A modified random-element isodisplacement model is used to describe the behavior of the optical phonons. The calculations of the dependence of the long-wavelength optical phonon frequencies on the composition are in good agreement with the experimental results.
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