Organometallic Vapor Phase Epitaxial Growth Research Articles

Heterostructures in GaInP grown using a change in V/III ratio

A natural monolayer {111} superlattice (the CuPt ordered structure) is formed spontaneously during organometallic vapor phase epitaxial (OMVPE) growth of Ga0.52In0.48P. The extent of this ordering process is found to be a strong function of the input partial pressure of the phosphorus precursor during growth due to the effect of this parameter on the surface reconstruction and step structure. Thus, heterostructures can be produced by simply changing the flow rate of the P precursor during growth. It is found, by examination of transmission electron microscope (TEM) and atomic force microscope (AFM) images, and the photoluminescence (PL) and PL excitation (PLE) spectra, that order/disorder (O/D) (really less ordered on more ordered) heterostructures formed by decreasing the partial pressure of the P precursor during the OMVPE growth cycle at a temperature of 620 °C are graded over several thousands of Å when PH3 is the precursor. The ordered structure from the lower layer persists into the upper layer. Similarly, D/O structures produced by increasing the PH3 flow rate yield PL spectra also indicative of a graded composition at the heterostructure. The grading is not reduced by a 1 h interruption in the growth cycle at the interface. Similar heterostructures produced at 670 °C using tertiarybutylphosphine (TBP) as the P precursor show a totally different behavior. Abrupt D/O and O/D heterostructures can be produced by abruptly changing the TBP flow rate during the growth cycle. PL and PLE studies show distinct peaks closely corresponding to those observed for the corresponding single layers. TEM dark field images also indicate that the interfaces in both for D/O and O/D heterostructures are abrupt. The cause of the difference in behavior for TBP and PH3 is not clear. It may be related to the difference in temperature.

Correlation between surface structure and ordering in GaInP

Ga and In atoms in Ga0.52In0.48P layers spontaneously segregate to form alternating In- and Ga-rich {111} monolayers during organometallic vapor phase epitaxial (OMVPE) growth on (001) oriented GaAs substrates, thus forming the CuPt ordered structure. This ordering phenomenon is believed to be driven by surface processes, although little direct experimental information is available. This work presents evidence, based on surface photoabsorption data, that [1̄10] oriented P dimers are present on the surface during OMVPE growth using trimethylgallium and ethyldimethylindium combined with tertiarybutylphosphine, suggesting a (2×4)-like surface reconstruction. Furthermore, when the growth temperature is increased above 620 °C, with other parameters constant, both the concentration of these P dimers and the degree of order are observed to decrease. A similar correlation of decreased P-dimer concentration with decreased degree of order is observed for decreases in V/III ratio. Thus, the changes in order parameter for variations in temperature and TBP flow rate are found to be closely correlated with the changes in the order parameter. A third parameter studied was the misorientation of the substrate from (001) toward either the {111}A or {111}B planes. The concentration of P dimers decreased as the misorientation increased in either direction. The degree of order was also observed to generally decrease, supporting the connection between surface reconstruction and ordering. However, the difference in order parameter observed for the two misorientation directions suggests the importance of a second parameter, the step structure, itself. For exactly (001) oriented substrates the surface was observed, using high resolution atomic force microscopy, to consist of islands, elongated in the [110] direction, with heights of 30–60 Å. Monolayer steps are observed for some growth conditions, but for most conditions the boundaries are formed exclusively of bilayer (5.7 Å) steps. Predominantly monolayer steps are formed for low V/III ratios and bilayer steps for high V/III ratios.

OMVPE growth of InAsSb using novel precursors

InAs, InSb, InAsSb and the related bismuth containing alloys are useful materials for infrared applications. A significant effort has been expended to develop new group III and group V precursors for organometallic vapor phase epitaxial (OMVPE) growth of these materials at low temperatures. We report the first use of a rarely studied group III source, triisopropylindium (TIPIn), together with the novel As and Sb precursors tertiarybutylarsine (TBAs) and tertiarybutyldimethylantimony (TBDMSb) for the growth of InAs and InAsSb epitaxial layers by atmospheric pressure OMVPE. InAs layers with good surface morphologies were obtained for growth temperatures as low as 300°C and low values of frsol|V/III ratio. Use of a high total flow rate and a reactor having a small volume upstream of the substrate alleviates the parasitic reaction problems reported earlier. This results in 3–5 × increase in the growth efficiency. Values of room temperature electron concentration, n, for InAs samples were found to range between 3 × 10 18 cm −3 for layers grown at 300°C to 9 × 10 16 cm −3 for layers grown at 400°C. These values of n are about an order of magnitude less than previously reported for InAs grown at the same temperature using either TMIn or EDMIn with AsH 3 or TBAs. InAs 1− x Sb x (0 < x < 0.7) layers were grown at 350°C with excellent surface morphologies for low frsol|V/III ratios. The layers have free electron concentrations ranging from 9 × 10 16 to 4 × 10 17 cm −3. X-ray diffraction data and 10 K photoluminescence spectra indicate that both the InAs and InAsSb layers grown at low temperatures using the new precursor combination are far superior to layers grown using other precursors.

Step structure during organometallic vapor phase epitaxial growth of ordered GaInP

The nature of the steps on the nominally (00l)-oriented surface of Ga0.5In0.5P lattice matched to GaAs has been studied using high resolution atomic force microscopy. The layers were grown by organometallic vapor phase epitaxy (OMVPE) at a temperature of 620°C on substrates misoriented by angles,ϑm, from 0 to 9° toward the % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frpe0db9Lqpepeea0xd9q8as% 0-LqLs-Jirpepeea0-as0Fb9pgea0lrP0xe9Fve9Fve9qapdbaqaae% GaciGaaiaabeqaamaaeaqbaaGcbaGaei4waSLafGymaeJbaebacqaI% XaqmcqaIWaamcqGGDbqxaaa!482D! $$[\bar 110]$$ direction in the lattice. An array of bunched steps from 25 to 50A in height, depending on the substrate misorientation angle, is observed on the surface. An unusual feature of these bunched or super-steps, as compared to those seen for GaAs surfaces, is that they have relatively short lengths of a few thousand Angstroms. In addition, not all of the steps congregate into the surface steps. Thus, the surface consists of three “phases”: (001) flats, (11n) facets, and misoriented areas covered by an array of monolayer steps. The fraction of steps contained in the supersteps decreases monotonically as ϑm increases from 3 to 9°. Again, this differs from reports of the nature of GaAs surfaces grown under similar conditions where essentially all of the steps congregate into supersteps. The value of n for the (lln) facets also varies with misorientation angle: The angle between the (001) and the (lln) facets increases from approximately 11-12° for ϑm = 3° to nearly 30† for ϑm = 9°. An attempt was made to correlate the surface structure with ordering, which is observed to vary significantly with misorientation angle. The degree of order is found to increase monotonically with the fraction of steps forming supersteps.

Phenomenology of Zn diffusion and incorporation in InP grown by organometallic vapor-phase epitaxy (OMVPE)

The diffusion characteristics and incorporation characteristics of Zn dopants in OMVPE-grown InP are studied. The Zn diffusion constant depends strongly on concentration and increases by four orders of magnitude in the Zn concentration range 2×1018–8×1018 cm−3. This drastic concentration dependence of the Zn diffusion constant is shown to determine the Zn incorporation characteristics during OMVPE growth. A spread of Zn dopants into intentionally undoped regions may result at high Zn doping concentrations in InP.

Growth of GaSb using trisdimethylaminoantimony

The organometallic vapor phase epitaxial (OMVPE) growth of GaSb using a new Sb source, trisdimethylaminoantimony (TDMASb) is described for a wide temperature range between 450 and 600° C. Good surface morphologies were obtained at low V III ratios due to the effective pyrolysis of TDMASb. High growth efficiencies were observed at growth temperatures as low as 475° C. As the growth temperature was decreased, the incomplete decomposition of trimethylgallium (TMGa) was found to lower the optimum V III ratio necessary to produce layers with good surface morphologies. The as-grown, unintentionally doped GaSb layers were p-type with background carrier concentrations of approximately 10 17 cm −3. Well resolved 15 K photoluminescence spectra and X-ray diffraction data indicate the GaSb layers to be of high quality for the growth temperature range studied. The results indicate that TDMASb is an excellent precursor for the OMVPE growth of GaSb over a wide range of growth temperatures.

Incorporation of Zn in GaAs during organometallic vapor phase epitaxy growth compared to equilibrium

The zinc concentration measured after organometallic vapor phase epitaxy (OMVPE) growth on (100)-oriented GaAs at 700 °C has been compared to the zinc concentration measured after in-diffusion under near-equilibrium conditions. During diffusion, the concentration of Zn 20 nm below the surface was found to vary with P1/2Zn, as expected for bulk solid–vapor equilibrium. During growth, the concentration of Zn varied linearly with PZn up to a maximum value which was found to correspond to the solubility limit set by second phase formation, e.g., growth of Zn3As2. Although large differences were observed between the results of the two experiments when using nominally identical ambient conditions, all of the results are consistent with a thermodynamic model in which the Fermi level at the surface is pinned approximately 200 meV below the intrinsic Fermi level. Typical OMVPE growth conditions appear to give a bulk zinc concentration which is supersaturated relative to the ambient partial pressures used, and to enhance the diffusion of Zn into the substrate.

Compositional Ordering in GalnP for Heterostructure Formation

AbstractCompositional ordering is observed in essentially all IIIN semiconductor alloys. The mechanism leading to the specific ordered structures formed is only now beginning to be understood. It is intimately related to the atomic-scale physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps. This paper will emphasize the use of surface analytic techniques to better understand the ordering processes during organometallic vapor phase epitaxial growth of GalnP. Surface photo absorption has been used to determine, for the first time, that the surface reconstruction is (2×4)-like during growth of GalnP with Cu-Pt ordering. By increasing the growth temperature and/or decreasing the V/Ill ratio the concentration of phosphorus dimers characteristic of the (2×4) structure is observed to decrease in tandem with a decrease in the degree of order measured in the epitaxial layers. This suggests that formation of the (2×4) reconstruction is necessary for formation of the Cu-Pt ordered structure.Atomic force microscopy was used to examine the step structure. For exactly (001)-oriented substrates, growth at low V/Ill ratios produces islands surrounded by single monolayer steps. Increasing the V/Ill ratio leads to the formation of bilayer steps approximately 6 Å high. A similar change in the structure of steps is observed in the vicinal regions for substrates misoriented to produce [110] steps. This phenomenon is interpreted in terms of the stabilization, at high V/Ill ratios, of the (2×2) reconstruction on the (111)B regions of the bilayer steps. This may also have an effect on formation of the Cu-Pt ordered structure.By changing the substrate temperature or the input partial pressure of the phosphorus precursor, the degree of order and, hence, the bandgap energy of GalnP, can be modulated during growth. This has allowed the production of a variety of single and double heterostructures. The heterostructures produced by changing the temperature from 740 to 620°C and from 620 to 520°C are abrupt. The heterostructures formed by changing the phosphine flow rate are not. The ordered structure in the lower layer persists into the upper layer. This may be an indication of the importance of the step structure.

Order/disorder heterostructure in Ga 0.5In 0.5P with ΔEg = 160 meV

Ordering in Ga 0.5In 0.5P can be controlled by variations in the substrate temperature during organometallic vapor phase epitaxial (OMVPE) growth. Growth at 720°C at a rate of 0.5 μm/h is shown to produce completely disordered material, as evidenced by the transmission electron diffraction (TED) and the photoluminescence (PL) results. The ordering produced at a growth temperature of 620°C is found to depend strongly on the substrate misorientation. Transmission electron micrographs and TED patterns for misorientations of 0°, 3°, 6°, and 9° from (001) toward the [ 1 00] direction in the lattice show that increasing the misorientation from 0° to 3° leads to the elimination of one variant, the elimination of twin boundaries, and an overall increase in the degree of order. Further increases in the misorientation angle to 6° and 9° at this growth temperature lead to increasing disorder, although only one variant is formed and the distance between antiphase boundaries (APBs) increases monotonically with increasing θ m. This wide variation in ordering behavior has allowed the growth of an order/disorder heterostructure for a substrate misorientation of 3°. The heterostructure consists of a Ga 0.52In 0.48P layer 0.5 μm thick grown at 740°C followed by an ordered layer 0.4 μm thick grown at 620°C. The X-ray diffraction results show that both layers are precisely lattice-matched to the GaAs substrate. TED patterns show that the first layer is completely disordered and the top layer is highly ordered, with only a single variant. High resolution images indicate that the interface is abrupt, with no dislocations or other defects. 10 K PL shows two sharp and distinct peaks at 1.995 and 1.830 eV for high excitation intensities. The peak separation is even larger at lower excitation intensities. The two peaks come from the disordered and ordered material, respectively. The peak separation represents the largest energy difference between ordered and disordered material reported to date. This large energy difference, 6.6 kT at room temperature, may make such heterostructures useful for photonic devices such as light emitting diodes, lasers, and solar cells.

Organometallic vapor phase epitaxial growth of AlP/GaP monolayer superlattice using tertiarybutylphosphine

The growth interruption time in the organometallic vapor phase epitaxial growth of AlP/GaP layers using tertiarybutylphosphine is optimized for the realization of an AlP/GaP monolayer superlattice. In the growth interruption, there exists an optimum time (2 s) beyond which the full width at half-maximum (FWHM) of the x-ray diffraction satellite peaks of an (AlP)5/GaP)5 superlattice becomes broader. The monolayer (AlP)1/(GaP)1 superlattice is realized for the first time in a AlP/GaP system. An average heterointerface roughness of as small as 0.12 Å is estimated from the FHWM of the (001) diffraction peak of the (AlP)1/(GaP)1 superlattice.

Trisdimethylaminoantimony: a new Sb source for low temperature epitaxial growth of InSb

Many new Sb sources for organometallic vapor phase epitaxial (OMVPE) growth of low energy band gap III/V antimonides have been developed and tested. However, most of the precursors including trimethylantimony (TMSb), triisopropylantimony (TIPSb), diisopropylantimonyhydride (DIPSbH), and tertiarybutyldimethylantimony (TBDMSb) have significant drawbacks such as inefficient pyrolysis at low temperatures or high levels of carbon contamination in the materials produced. In this work, a new Sb source, trisdimethylaminoantimony (TDMASb) [Sb(N(CH 3) 2) 3], has been used with trimethylindium (TMIn) for the growth of InSb epitaxial layers by atmospheric pressure OMVPE. This precursor is found to be particularly effective at low growth temperatures. V/III ratios for growth of good morphology layers were less than 3 for growth temperatures of 300 to 425°C. A V /III ratio of less than 1 was optimum at 275°C since the TDMASb pyrolyzes more efficiently than TMIn at this temperature. Higher growth efficiencies (growth rate/group III molar flow rate) were observed than for other Sb precursors for growth temperatures below 400°C. From the photoluminescence (PL) spectra and X-ray diffraction data, it was confirmed that good InSb crystallographic quality was obtained for growth temperatures from 425 to as low as 275°C. For the first time, PL at 10 K has been observed from InSb epitaxial layers grown at 300°C. The free electron concentrations of the InSb epitaxial layers were measured to be between 2.7 × 10 16 and 5 × 10 17 cm -3 over the entire range of growth temperature. Thus, the very high levels of carbon incorporation measured for low-temperature growth using several other Sb precursors was avoided using TDMASb. These results indicate that the new Sb precursor, TDMASb, is excellent for OMVPE growth of InSb and appears to be the best source to date for low temperature growth.

Organometallic vapor phase epitaxial growth of p-type ZnSe using phenylhydrazine as the dopant source

The growth and nitrogen doping of ZnSe by photo-assisted organometallic vapor phase epitaxy (OMVPE) have been investigated using phenylhydrazine (PhHz) as the dopant source. The layers were characterized using photoluminescence (PL), secondary ion mass spectroscopy (SIMS) and capacitance-voltage ( C-V) measurements. A high incorporation of nitrogen was observed over the growth temperature range between 350 and 400°C, even when extremely low dopant partial pressure of 10 -8 atm was used. Typical layers had active acceptor concentrations of (1–2)X10 15 cm -3. Low temperature growth kinetics with the above dopant source were investigated and a possible model for the nitrogen incorporation is presented.

Nitrogen doping of ZnSe by OMVPE using a novel organometallic precursor

We have investigated phenylhydrazine (PhHz) as a potential nitrogen dopant source in organometallic vapor phase epitaxial growth of ZnSe. Dimethylzinc and dimethylselenide were the zinc and selenium precursors, respectively. Photoluminescence and secondary ion mass spectroscopy measurements indicate that high incorporation efficiency compared to ammonia can be achieved using this dopant source. For example, nitrogen incorporation in the 2.5 x 1018/cm-3 level was achieved at 350°C under ultraviolet excitation when the PhHz partial pressure was 1 x 10-8 atm. These layers had 1-2 x lO15cm-3 electrically active acceptors. Films grown at higher partial pressures of PhHz were highly compensated.

Growth of InAIGaAs strained quantum well structures for reliable 0.8 μm lasers

Incorporation of indium into the quantum well materials of graded-index separate confinement heterostructure quantum well lasers has proven to be a key to imparting a much needed robustness to such lasers. By growing wells which contain both indium and aluminum along with gallium, operating wavelengths can be engineered to fall in the technologically important range of 0.8 microns, appropriate for pumping Nd:YAG. The organometallic vapor phase epitaxial growth of these strained-layer structures faces extra challenges rooted in the competing influences on the energies of the quantized states. At a minimum, meeting wavelength targets requires achieving control of the quaternary composition and of the quantum well thickness. Because laser elements are relatively large, lateral uniformity of wavelength is a critical issue. Device performance is influenced by basic material quality, which is a function of such fundamental growth parameters as temperature, V/III ratio, and growth rate. We have grown InAIGaAs structures using various combinations of growth conditions and well composition and thickness combinations, and evaluated and life-tested lasers in CW mode. The reactor’s performance in achieving composition and thickness uniformity is reported, as are data on the influence of the effects of growth conditions on device performance.

Diisopropylantimonyhydride (DIPSbH) for low temperature epitaxial growth of InSb

Low growth temperatures are necessary for the organometallic vapor phase epitaxial growth of many III/V semiconductors, particularly the low energy band gap antimonides. This has caused difficulties with conventional, established precursors because of low pyrolysis efficiencies at low temperatures and large amounts of carbon contamination in the solid. This paper gives the first results of the use of a new precursor, diisopropylantimonyhydride (DIPSbH), (C 3H 7) 2SbH. It has been used with trimethylindium (TMIn) to produce InSb epitaxial layers at temperatures as low as 275°C with values of V/III ratio of approximately 2.5. In this regard, it is the best Sb precursor tested to date for low temperature growth. The morphology and crystallographic quality of the epitaxial layers are acceptable for semiconductor applications. Photoluminescence spectra could be measured for layers grown at 325°C and above. The spectra are similar to those from commercial InSb substrates. Van der Pauw measurements indicate that the free electron concentration of the InSb increases dramatically as the growth temperature is lowered. Layers grown at 300°C have donor densities in excess of 10 19 cm -3. The donor concentrations are much higher than for InSb grown using tertiarybutydimethylantimony, another low-temperature Sb precursor. SIMS measurements indicate that the donor is carbon.

Room-temperature operation of GaInAs/GaInAsP/InP SCH lasers with quantum-wire size active region

Improvements in the fabrication of GaInAs(P)/InP devices consisting of an ultrafine structure by using two-step organometallic vapor phase epitaxy (OMVPE) growth, electron beam exposure direct writing, and wet chemical etching are reported. This improved process achieved, for the first time, a room-temperature continuous-wave (CW) operation of GaInAs/InP quantum-wire lasers consisting of 5-nm-thick and 10-30-nm-wide vertically stacked triple quantum-wire active region within the period of 70 nm. A large blue shift of approximately 40 nm was observed in both the lasing and the electroluminescence spectra of Ga/sub 0.3/In/sub 0.7/As/InP compressively strained multi-quantum-well (MQW) wire lasers consisting of a 3-nm-thick and 30-60-nm-wide five-wire active region, which suggests a reduced effective mass of holes along the in-plane direction. >

Compositional Ordering in Semiconductor Alloys

AbstractCompositional ordering has been observed in a wide variety of III/V semiconductor alloys as well as in SiGe alloys. The thermodynamic driving force is now understood in terms of minimization of the microscopic strain energy of the bonds in the solid. However, the mechanism leading to the specific ordered structures formed is only now beginning to be understood. It appears to be intimately related to the physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps and kinks. Thus, an improved understanding the ordering process may lead to a better understanding of the surface processes occurring during epitaxial growth from the vapor.This paper will review the current understanding of the ordering process, including discussions of the arrangement of atoms on the surface and the nature of surface steps. The emphasis will be on the use of patterned surfaces to investigate and control the ordered structures formed during organometallic vapor phase epitaxial growth of GaInP. Using photolithography and chemical etching, [110]-oriented steps are formed on the (001) GaAs substrate. The direction of motion of these steps determines the specific variant of the Cu-Pt ordered structure (with ordering on (111) planes) formed. The step density at the edge of the groove apparently determines the degree of order. Highly stepped surfaces suppress ordering or lead to small domains of a single variant. When the steps are very shallow, the large domain of the predominant variant is filled with “inclusions” of the second variant. Step edges that are oriented at nearly 160 from (001) form a {511} variant during growth. This facet is observed to grow at the expense of adjacent (001) surfaces and to produce material that is completely disordered.Growing on intentionally misoriented substrates leads to interesting structures consisting of both large, highly-ordered domains and disordered material. This allows, using cathodoluminescence(CL) imaging, a direct determination of the effect of ordering on the energy band gap. In the GaInP samples studied, the CL images show that the disordered material has a distinct emission pattern consisting of a single, sharp peak at an energy more than 100 meV higher than that observed in the adjacent ordered region.

Triisopropylindium: decomposition study and use for low temperature growth of InAs

The organometallic vapor phase epitaxial (OMVPE) growth of In-containing III–V semiconductors typically uses trimethylindium (TMIn). However, TMIn suffers from several problems. First, it is well known that the effective vapor pressure of solid TMIn changes with time because of changes in the surface area. Secondly, TMIn decomposes slowly for temperatures lower than 400°C in an atmospheric pressure OMVPE reactor; it is too stable for somelow-temperature applications. In addition, it causes carbon contamination, especially at low temperatures, due to the CH 3 radicals. Thus, there is a need for new In precursors that are liquids at room temperature and do not contain CH 3 radicals. This work reports the first decomposition and OMVPE growth studies for a newly developed indium source, triisopropylindium (TIPIn). The decomposition study was carried out in an isothermal flow tube reactor with the reaction products analyzed using a mass spectrometer. The temperature for 50% decomposition is ∾ 110°C for TIPIn in a He ambient. This is about 200°C lower than that for TMIn under similar conditions. The mass spectroscopic peaks occur at m/ e = 39, 42, 43, 71, and 86. The relative intensities indicate that the major product for TIPIn decomposition is C 6H 14. This suggests that TIPIn decomposes by homolysis, producing C 3H 7 radicals that mainly recombine to produce C 6H 14. The OMVPE growth study was carried out in an atmospheric pressure OMVPE reactor in H 2 with AsH 3 as the As source. InAs epilayers with good surface morphologies were obtained for temperatures as low as 300°C at a V/III ratio of 460. The necessary V/III ratio increases as the growth temperature is decreased, due to the incomplete decomposition of AsH 3 at low temperatures. The less reactive C 3H 7 radicals from TIPIn pyrolysis produce far less carbon in the solid than the more reactive CH 3 radicals produced by TMIn pyrolysis. A disadvantage of TIPIn is the low growth efficiency, due to parasitic reactions. Thus, it appears that TIPIn may be best suited for low pressure OMVPE or, particularly, for chemical beam epitaxy.

Tertiaybutyldimethylantimony for GaSb growth

Antimony-containing alloys have the lowest energy bandgaps of the conventional III-V semiconductors. Organometallic vapor phase epitaxy (OMVPE) has proven to be an effective and convenient technique for the production of the antimony alloys, normally using trimethylantimony (TMSb) as the antimony source. However, TMSb has several problems: (a) it decomposes at relatively high temperatures due to the strong CH3-Sb bond, and (b) its use results in carbon contamination from the active methyl radicals, especially for the growth of aluminum-containing alloys. Recently, tertiarybutyldimethylantimony (TBDMSb) has been successfully used to grow high quality InSb epitaxial layers at temperatures as low as 325°C with low V:III ratios. This paper reports the use of TBDMSb to grow GaSb layers at temperatures from 500° to 650°C. Group V:III ratios close to unity are required for good surface morphologies. The optimum V:III ratio decreases slightly as the growth temperature is lowered due to the incomplete decomposition of trimethylgallium (TMGa). The growth efficiency is about 1 × 104 μm/mole, indicating that there are no significant parasitic reactions between TMGa and TBDMSb. The as-grown layers are p-type. The background carrier concentration is nearly independent of growth temperature. Low temperature (10K) photoluminescence (PL) intensities are also nearly independent of temperature in this range. The PL spectra consist of two peaks, a bound exciton peak at about 792 meV and a native acceptor complex (VGa, GaSb) peak at about 775 meV. At every growth temperature, the ratio of the PL intensity of the bound exiton peak to the native acceptor peak is always higher for samples grown using optimum conditions. The results show that TBDMSb can be used for the OMVPE growth of antimony-containing materials over a wide range of growth temperature.

The effect of GaAs surface stabilization on the properties of ZnSe grown by organometallic vapor phase epitaxy

Organometallic vapor phase epitaxial growth of ZnSe on GaAs was carried out using dimethylzinc (DMZn) and dimethylselenide (DMSe) as the reactants. Unlike III–V systems, where growth is always started by first introducing columm V precursor, the growth of ZnSe can be initiated either by introducing DMZn first (Zn-stabilization) or DMSe first (Se-stabilization). A systematic study of the properties of ZnSe epilayers, grown under these two surface stabilization conditions, was carried out using photoluminescence (PL) and double crystal X-ray diffraction (DCD). Layers grown on Se-stabilized substrates exhibited superior photoluminescence spectrum, but had higher X-ray full width at half maximum (FWHM) compared to those grown on Zn-stabilized surfaces. Detailed studies revealed that layers grown on Se-stabilized surfaces were titled with respect to the substrate. A possible cause for the differences in the ZnSe layers grown on these two surfaces is proposed.