D. H. Jaw

Photoluminescence of InSb, InAs, and InAsSb grown by organometallic vapor phase epitaxy

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.

Atomic ordering in GaAsP

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 (111) and (111) 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 (111) plane, appears for epilayers grown on substrates misoriented by 6° towards [110]. These ordering‐induced spot...

Organometallic vapor phase epitaxial growth and characterization of InAsBi and InAsSbBi

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 w...

Raman scattering in AlxGa1-xAsySb1-y quaternary alloys

The Raman scattering of AlGaAsSb quaternary alloy semiconductors has been investigated for the first time. The AlGaAsSb quaternary alloys, including the AlGaSb ternary alloys, were grown by organometallic vapor phase epitaxy. The dependence of the long‐wavelength longitudinal‐optical phonon frequencies on the composition are reported. The first‐order Raman spectra show a two‐mode behavior for the AlGaSb ternary alloys and a three‐mode behavior for the AlGaAsSb quaternary alloys. For AlGaAsSb, two peaks located below 300 cm−1 are assigned as the GaAs‐ and GaSb‐like LO modes. Two peaks observed above 300 cm−1 are assigned as the ‘‘AlAs plus AlSb’’ LO and TO modes. A broad peak observed below 200 cm−1 is assigned as a disorder‐activated acoustic phonon mode.

Long‐wavelength lattice dynamics of GaxIn1−xAsySb1−y quaternary alloys

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.

Effects of substrate misorientation on ordering in GaAs0.5P0.5 grown by organometallic vapor phase epitaxy

Effects of (001) GaAs substrate misorientation on the formation of the group V sublattice {111} (CuPt) ordered structure are studied for the first time for GaAs0.5P0.5. It is found that the direction of substrate misorientation has a strong effect on the determination of which variants are formed. Two of the four possible ordered variants appear for epilayers grown on exact (001) substrates. The same two variants also appear for the epilayers grown on the (001) substrates misoriented by 6° towards [110]. Only one variant appears on epilayers grown on (001) substrates misoriented by 6° towards the [110] direction. Most significantly, all the ordered‐induced diffraction spots in GaAsP are found to occur on the [110] cross section. Thus, the variants found in GaAsP are exactly the same as for GaInP, an alloy with CuPt ordering on the group III sublattice. This result is contradictory to expectations based on the bond‐length model proposed previously for GaInP alloys. In addition, for all the 6° misorientate...

Organometallic vapor phase epitaxial growth of a new quarternary semiconductor alloy Ga1−xInxP1−ySby

Abstract Quaternary Ga 1− x In x P 1− y Sb y alloys have been grown for the first time by atmospheric pressure organometallic vapor phase epitaxy (AP-OMVPE) in a horizontal, infrared-heated reactor using trimethylgallium, trimethylindium trimethylantimony, and phosphine as the source materials. In general, epilayers with good surface morphologies were obtained. Growth temperatures between 480 and 560°C were used because of the low melting temperatures of these alloys. At the lower end of this range, Ga incorporation was found to decrease with decreasing temperature. Furthermore, the presence of Sb in the growth process also caused a decrease of the Ga distribution coefficient. Optical characterization was carried out using low temperature photoluminescence, photoluminescence excitation, and transmission spectroscopies. Quaternary alloys with 10 K energy band gaps ranging from 0.21 to 1.98 eV (5.9 to 0.63 μm) were grown on GaAs, InP, GaSb, InAs, and InSb substrates. The band gap energies were found to be in good agreement with the results of earlier calculations. However, 10 K photoluminescence of Ga 1− x In x P 1− y Sb y with higher band gaps was routinely observed with peak energies about 90 to 140 meV lower than the band gap energies. This may be due to either donor-acceptor pair recombination or, perhaps, recombination involving tail states produced by compositional fluctuations in these highly metastable alloys. Smaller band gap alloys have peak energies lower than the values of band gap by about 20 to 110 meV.

Atomic ordering in InAs0.5P0.5 grown by organometallic vapor phase epitaxy

InAsP epilayers grown by organometallic vapor phase epitaxy have been investigated using transmission electron microscopy. Electron diffraction studies using 〈110〉 cross sections indicate the formation of CuPt‐like ordering on the group V sublattice. Only two of the four possible ordered variants are observed for epilayers grown on the exactly (001) oriented InP substrates. All the order‐induced diffraction spots for InAsP are found to occur on the [110] cross section. Thus, the variants found in InAsP are 1/2(111) and 1/2(111), exactly the same as those found in GaInP, an alloy with CuPt ordering on the group III sublattice. This result is in agreement with recent studies on GaAsP and is contradictory to expectations based on the bond‐length model proposed previously for GaInP alloys. The direction of substrate misorientation has a strong effect on the formation of ordered structures for normally (001) oriented InP substrates.

Radical‐assisted organometallic vapor‐phase epitaxial growth of GaAs

For the first time, radicals have been added to assist organometallic vapor‐phase epitaxial (OMVPE) growth of GaAs at low temperatures. Supplemental t‐C4H9 radicals from the pyrolysis of azo‐t‐butane [(t‐C4H9)2N2] were used to increase the growth rate of GaAs from trimethylgallium [TMGa, (CH3)3Ga] and arsine (AsH3) at temperatures as low as 390 °C. Mass spectroscopy studies show that the added radicals enhance the decomposition rates of both TMGa and AsH3. The GaAs growth rate was increased by a factor of 6 at 450 °C. The radical‐assisted OMVPE grown samples are, indeed, GaAs based on microprobe analysis. Spectra from Raman scattering experiments further confirm that the GaAs is single crystalline.

Optical properties of Ga1-xInxP1-ySby alloys grown by organometallic vapor phase epitaxy

The new family of GaInPSb quaternary alloys grown by organometallic vapor phase epitaxy was characterized by photoluminescence, transmission, photoluminescence excitation, and Raman spectroscopies. Transmission and photoluminescence excitation spectroscopic techniques were applied to determine the energy band gap of the alloys. It was found that the values of band gap obtained for the GaInPSb alloys were close to the theoretical values deduced from the data obtained for the end ternary alloys. The photoluminescence peak energies for all the samples were found to be about 80 to 150 meV below the band gap deduced from the transmission measurements. The large difference between the photoluminescence peak energy and band gap, together with other evidence, suggests that the photoluminescence is from recombination involving a deep center. The long wavelength lattice dynamics of the alloys were studied by Raman spectroscopy in the wave‐number range from 150 to 400 cm−1. The long wavelength optical phonons displayed a ‘‘three‐ and four‐mode’’ behavior.