Z. M. Fang

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.

Organometallic vapor-phase epitaxy growth and characterization of Bi-containing III/V alloys

For potential infrared detector applications, single‐crystalline InAsBi and InAsSbBi have been grown by atmospheric pressure organometallic vapor‐phase epitaxy. The precursors used were trimethylindium, trimethylantimony, trimethylbismuth, and arsine at growth temperatures of 375 and 400 °C. Good quality epilayers with smooth surface morphologies were obtained by properly controlling the key growth parameter, the V/III ratio. The variation of lattice constant with solid composition for the InAs1−xBix system, a=6.058+0.966x, provides evidence that Bi atoms indeed incorporate substitutionally into the As sites of the sublattice in the InAs zinc‐blende structure. An extrapolated lattice parameter for the hypothetical zinc‐blende InBi is 7.024 A. Thermodynamic calculations of the InAs‐InBi and InSb‐InBi pseudobinary phase diagrams were carried out using the delta‐lattice‐parameter model using the lattice constant for zinc‐blende InBi of 7.024 A. The results agree well with experimental data. The calculations ...

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...

Effect of growth temperature on photoluminescence of InAs grown by organometallic vapor phase epitaxy

Infrared photoluminescence (PL) from InAs epitaxial layers grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) has been studied as a function of the growth temperature (350–600 °C). It is shown that the PL spectra depend strongly on the growth temperature. The integrated PL intensity decreases by about two orders of magnitude as the growth temperature decreases from 500 to 350 °C. In addition, Hall‐effect measurements show that the n‐type impurity concentration in InAs increases rapidly as the growth temperature decreases. The results of secondary‐ion mass spectroscopy show that the dominant impurity is carbon and its concentration varies with the growth temperature in a similar way to the electron concentration. This confirms that carbon is a donor in InAs. The decreasing PL intensity with decreasing growth temperature is attributed to the increasing carbon concentration.

Investigation of organometallic vapor phase epitaxy of InAs and InAsBi at temperatures as low as 275 °C

InAs and InAsBi have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) over a broad temperature range from 600 to as low as 275 °C. This is the lowest growth temperature ever reported for standard OMVPE. It is demonstrated that lowering the growth temperature is the most effective approach for increasing the Bi content in InAsBi alloys. For example, InAsBi samples with Bi concentrations as high as 6.1 at.% have been successfully grown at a temperature of 275 °C. Trimethylindium, arsine, and trimethylbismuth were used as precursors for most experiments. The growth efficiency is a constant for temperatures above 400 °C, indicating the growth rate is diffusion limited in this temperature regime. For lower temperatures, it decreases exponentially with decreasing temperature with an activation energy of 24 kcal/mol. Incomplete pyrolysis of TMIn limits the growth rate in this temperature regime. However, by substituting ethyldimethylindium for TMIn the diffusion controlled regime can...

Photoluminescence of InAsBi and InAsSbBi grown by organometallic vapor phase epitaxy

Infrared photoluminescence (PL) from InAsBi and InAsSbBi epitaxial layers grown by atmospheric pressure organometallic vapor phase epitaxy has been studied. The PL from ternary InAsBi was investigated for Bi concentrations of ≤2.3 at. %. The peak energy decreases at a rate of 55 meV/at. % Bi with increasing Bi concentration. A study of the transmission spectra of these Bi‐containing alloys confirms the above result. The PL peak is assigned to near band edge emission for InAsBi. The value of dEg/dx=−55‐meV/at. % Bi is more than double the previously reported theoretical prediction for the band gap of InAsBi. The PL for the quaternary layer of InAsSbBi is also studied for Sb concentrations of <10 at. % and Bi concentrations of ≤1.5 at. %. Bi incorporation in InAs1−xSbx(0.07<x<0.10) reduces the PL peak energy at a rate of 46‐meV/at. % Bi. These results imply that incorporation of only a few percent of Bi is required in InAs0.35Sb0.65 to achieve a band gap of 0.1 eV, equivalent to a wavelength of 12 μm, desir...

Surface quantum wells

Surface quantum wells of InP have been grown, by organometallic vapor phase epitaxy, on top of graded GaxIn1−xP epitaxial layers. The surface quantum well is confined on one side by vacuum, and on the other side by the graded GaxIn1−xP. Photoluminescence measurements show two transitions for electron‐hole recombination within the surface quantum well. Surface recombination appears to be saturated by the high density of carriers collected in the well, and plays a minor role. The bending of the conduction and valence bands in the GaxIn1−xP leads to a high collection efficiency of excess carriers near the surface, and suggests that high efficiency surface light emitters could be built in similar structures.

Triisopropylantimony for organometallic vapor phase epitaxial growth of GaSb and InSb

In the past, trimethylantimony (TMSb) has been almost exclusively used as the Sb source in organometallic vapor phase epitaxy (OMVPE). However, TMSb decomposes at relatively high temperatures (above 500 °C). For growth at lower temperatures, TMSb is not an optimum choice. In addition, TMSb decomposition produces methyl radicals, a source for carbon contamination. Thus, it is important to investigate alternative Sb precursors. In this letter, we report the use of a newly developed Sb source, triisopropylantimony (TIPSb), for atmospheric pressure OMVPE. It is found that both GaSb and InSb can be grown with good surface morphologies at temperatures between 430 and 600 °C. The high growth efficiencies indicate that there are few parasitic reactions between TIPSb and trimethylgallium (TMGa) or trimethylindium (TMIn). The GaSb layers grown at 500 °C have background hole concentrations of 2×1016 cm−3. Low‐temperature photoluminescence (PL) measurements indicate that the acceptor is due to Sb vacancies rather tha...

Ultra-low temperature OMVPE of InAs and InAsBi

InAs and InAsBi have been grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) over a broad temperature range from 600 to as low as 275° C. This is the lowest growth temperature ever reported for conventional OMVPE. It is demonstrated that lowering the growth temperature is the most effective approach for increasing the maximum Bi content in InAsBi alloys where the Bi solubility limit is 0.025 at.%. For example, InAsBi samples with Bi concentrations as high as 6.1 at.% have been successfully grown at a temperature of 275° C. Trimethylindium, arsine, and trimethylbismuth were used as precursors for most experiments. The growth efficiency is a constant for temperatures above 400° C, indicating that the growth rate is diffusion limited. For lower temperatures, it decreases exponentially with decreasing temperature with an activation energy of 24 kcal/mol. Incomplete pyrolysis of TMIn limits the growth rate in this temperature regime. By substituting ethyldimethylindium for TMIn the growth rate can be increased at lower temperatures. Hall effect measurements show that then-type background concentration increases from approximately 2.3 × 1016 to 1019 cm−3 as the growth temperature decreases from 600 to 325° C. Secondary ion mass spectroscopy results show that the dominant impurity is carbon. Thus, carbon is mainly a donor in these materials. The integrated photoluminescence intensity drops rapidly with decreasing growth temperature.

The use of triisopropylantimony for the growth of InSb and GaSb

A newly developed Sb source, triisopropylantimony (TIPSb), has been successfully used to grow InSb and GaSb epilayers by atmospheric pressure organometallic vapor phase epitaxy (OMVPE). Both GaSb and InSb have been grown with excellent morphologies. Growth efficiencies indicate that there are no parasitic reactions between TIPSb and trimethylgallium (TMGa) or trimethylindium. For GaSb growth, the temperatures have been varied between 500 and 600 °C. V/III ratios close to unity are necessary to obtain the best morphologies at 600 °C. As the growth temperature is decreased, lower V/III ratios are required. This is because TMGa decomposition is incomplete and TIPSb decomposes completely at these temperatures. The GaSb layers grown at 500 °C have background hole concentrations of 2×1016 cm−3. Low‐temperature photoluminescence (PL) measurements indicate that the acceptor is due to Sb vacancies rather than carbon acceptors. A major advantage of TIPSb is that it decomposes at temperatures much lower than that fo...