Growth Rate Of GaSb Research Articles

Photoluminescence properties as a function of growth mechanism for GaSb/GaAs quantum dots grown on Ge substrates

In this work, we use photoluminescence (PL) spectroscopy to investigate how self-assembled GaSb/GaAs quantum dots (QDs) depend on their growth mechanism. Carrier transfer (i.e., carrier recombination in QDs and escape through the barrier layer) is investigated as a function of excitation-power- and temperature-dependent PL measurements. A drastic blueshift of the QD peak energy from 1.23 to 1.30 eV and a further shift to 1.33 eV reveal the influence of the GaSb growth rate and the growth temperature on the optical properties of these QDs. The thermal activation energy is extracted from the temperature-dependent PL by fitting the integrated PL intensity of the QD peaks to the Arrhenius relation. The QDs grown at the growth rate of 0.1 monolayers/s at 450 °C have higher thermal activation energy (109 meV) than those grown at a lower growth rate and higher QD growth temperature. The observed PL characteristics are discussed in terms of QD size, uniformity of QDs, and material intermixing occurring during QD growth on the buffer layer and capping layer.

High-Mobility GaSb Nanostructures Cointegrated with InAs on Si

GaSb nanostructures integrated on Si substrates are of high interest for p-type transistors and mid-IR photodetectors. Here, we investigate the metalorganic chemical vapor deposition and properties of GaSb nanostructures monolithically integrated onto silicon-on-insulator wafers using template-assisted selective epitaxy. A high degree of morphological control allows for GaSb nanostructures with critical dimensions down to 20 nm. Detailed investigation of growth parameters reveals that the GaSb growth rate is governed by the desorption processes of an Sb surface layer and, in turn, is insensitive to changes in material transport efficiency. The GaSb crystal structure is typically zinc-blende with a low density of rotational twin defects, and even occasional twin-free structures are observed. Hall/van der Pauw measurements are conducted on 20 nm-thick GaSb nanostructures, revealing high hole mobility of 760 cm2/(V s), which matches literature values for high-quality bulk GaSb crystals. Finally, we demonstrate a process that enables cointegration of GaSb and InAs nanostructures in close vicinity on Si, a preferred material combination ideally suited for high-performance complementary III-V metal-oxide-semiconductor technology.

A study of the growth rate of GaSb using TEGa and TMSb or TESb

The growth rate of gallium antimonide using triethylgallium and either trimethylantimony or triethylantimony has been studied over a wide temperature range, from 475 to 675°C. In contrast to earlier reports of the growth being diffusion controlled when trimethylantimony is used, we find that it is kinetically controlled at temperatures below 650°C. The growth rate of gallium antimonide when trietylantimony is used varies in a complex way with temperature but is ultimately diffusion controlled above 650°C, with both trimethylantimony and triethylantimony yielding the same growth rate. For comparison, the growth rate of gallium arsenide was studied with triethylgallium and arsine or tertiarybutylarsine, and with trimethylgallium and arsine: in both case, it is diffusion controlled in the entire temperature range studied. However, the diffusion controlled growth rate of gallium antimonide predicted from the gallium arsenide growth rate is lower than what is experimentally observed.

Selective GaSb radial growth on crystal phase engineered InAs nanowires.

In this work we have developed InAs nanowire templates, with designed zinc blende and wurtzite segments, for selective growth of radial GaSb heterostructures using metal organic vapor phase epitaxy. We find that the radial growth rate of GaSb is determined by the crystal phase of InAs, and that growth is suppressed on InAs segments with a pure wurtzite crystal phase. The morphology and the thickness of the grown shell can be tuned with full control by the growth conditions. We demonstrate that multiple distinct core-shell segments can be designed and realized with precise control over their length and axial position. Electrical measurements confirm that suppression of shell growth is possible on segments with wurtzite structures. This growth method enables new functionalities in structures formed by using bottom-up techniques, with complexity beyond that attainable by using top-down techniques.

Growth behavior of GaSb by metal–organic vapor-phase epitaxy

The growth mechanisms of GaSb in a metal–organic vapor-phase epitaxy (MOVPE) system were studied for both trimethyl gallium (TMG)/trimethyl antimony (TMSb) and triethyl gallium (TEG)/TMSb growth chemistries. The effect of growth temperature and precursor mole fractions on GaSb growth rate was determined experimentally. Numerical analysis of the reactor and growth process was described in a combined chemical–thermal–fluid flow model. A Langmuir–Hinshelwood-type mechanism involving a surface reaction between adsorbed monomethyl gallium (MMG) and adsorbed monomethyl antimony (MMSb) or adsorbed Ga and adsorbed MMSb was proposed for the growth of GaSb by MOVPE using TMG or TEG and TMSb chemistries, respectively. The chemical model for TMG/TMSb chemistry included bounds on the surface chemistry derived for the range of V/III precursor ratio which were observed to lead to a second phase, i.e., elemental Ga or Sb, formation. Two growth regimes were observed for TMG/TMSb chemistry: above 575 °C the growth rate was mass transfer controlled whereas for lower temperatures it is kinetically limited. No such temperature dependence has been found for the TEG/TMSb chemistry over all experimental employed ranges of growth parameters.

Metalorganic chemical vapor deposition growth of high-quality InAs∕GaSb type II superlattices on (001) GaAs substrates

InAs layers and InAs∕GaSb type II superlattices (SLs) were grown on (001) GaAs substrates by metalorganic chemical vapor deposition. A thin low-temperature GaSb nucleation layer and a thicker high-temperature metamorphic GaSb buffer layer were introduced before the growth of InAs or the SLs. By optimizing the growth temperature, the interface gas switching and the growth rate, morphology, and structural properties of the grown structures are significantly improved. In some cases, nanopipes are found in these structures. Morphology studies of the InAs heteroepitaxial layers show that (1) the diameter of these nanopipes decreases with the growth temperature; (2) nanopipes are nucleated from the interface of GaSb∕InAs; and (3) the density of nanopipes depends on the passivation of GaSb surface before the growth of the InAs. In growing InAs∕GaSb SLs, we show that the growth rate of GaSb has a strong effect on the morphology and that the unintentional interfacial InSb layer formed at the InAs∕GaSb interfaces is the origin of the nanopipes. Through the optimization of the growth parameters, high-quality 100-period SLs without nanopipes and with good optical absorption in 3–8μm infrared region have been realized.

Metal organic chemical vapor deposition of metaphorphic InAs–GaSb superlattices on (0 0 1) GaAs substrates for mid-IR photodetector applications

InAs/GaSb superlattices (SLs) were grown on (0 0 1) GaAs substrates by metal organic chemical vapor deposition. A thin low temperature (LT) GaSb nucleation layer followed by a 250 nm thick high temperature (HT) GaSb buffer layer were introduced before the growth of the SLs and their growth conditions were optimized. The effects of growth temperature and GaSb growth rate on the morphology and structural properties of the SL were systematically studied. Atomic force microscopy, photoluminescence, transmission electron microscopy and X-ray diffraction were used to characterize the grown structures. Generally, nanopipes, about 100 nm in diameter, were found in the grown structures and their formation depends strongly on the growth temperature and the GaSb growth rate in growing the SL. By optimizing these parameters, high-quality InAs/GaSb SLs without nanopipes and with sharp interfaces have been realized.

Effect of Substrate Orientation on the Growth Rate and Surface Morphology on GaSb Grown by Metal-Organic Vapor Phase Epitaxy

AbstractMOVPE of GaSb grown on (100), (111)A and (111)B GaSb substrates were investigated to study the effect of substrate orientation on the growth rate and surface morphology. Besides growth temperature and V/III ratio, the GaSb growth rate strongly depends on the crystallographic orientation. As the V/III ratio rises, the growth rate on the (111)B oriented substrate decreases, whereas that on the (111)A oriented substrate increases. The surface morphology on different substrates was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). On (111)A substrates, triangular hillocks are the dominant defects, while on (111)B planes, three distinct types of hexagonal hillocks are observed, namely, non-flat top hexagonal structure with spiral growth features (Type I), flat top structure with lateral growth features (Type II), and non-flat top hexagonal structure with multiple islands (Type III). For all types, the basal edges of each hillock are preferentially aligned along <110> directions. A closer look reveals that the top surface of Type II feature consists of many levels of small hexagonal shaped terraces, with each step height in the monolayer range, indicating a step flow growth involved.

Growth of resonant interband tunneling diodes using trimethylamine alane

Resonant interband tunneling diodes (RITDs) in the (Al,Ga)Sb InAs material system have been studied recently for use in a new class of multifunctional quantum devices. The RITD consists of InAs contacting regions and an AlSb/GaSb/AlSb QW structure in the active region, and make use of the type-II energy band alignment between InAs and GaSb. Conventional solid-source MBE is typically used to grow these RITDs, and a high peak-to-valley current ratio (PVCR) can be achieved at room temperature. In this study, we report and compare the electrical properties of RITDs grown using elemental as well as alkyl Al and Ga sources. Arsine and solid Sb were used for Group V sources, while trimethylindium was used throughout to grow the InAs layers. Using trimethylamine alane as the Al source, PVCRs comparable to those obtained by using elemental Al have been obtained. However, the additional substitution of triethylgallium for elemental Ga resulted in a sizeable reduction in the PVCR. The strong dependence of the GaSb growth rate on substrate temperature and V III flux ratio is believed to be a likely cause of the degradation.

Metalorganic molecular beam epitaxy of GaSb on patterned GaSb substrates using triethylgallium and Sb 4

The MOMBE (metalorganic molecular beam epitaxy) growth of GaSb on GaSb substrates with different orientations, (100), (511), (411), (311), (211) and (111), and on patterned (100) GaSb substrates was investigated for the first time using TEG and Sb 4 as source materials. With increasing substrate temperatures from 450 to 600°C, the growth rate of GaSb shows a strong increase on the (511)B, (411)B and (311)B substrates. The maximum growth rate of GaSb was obtained on the (411) planes at T sub ⪢ 500° C. Increase of the growth rate on (511)B, (411)B and (311)B surfaces is explained by an enhanced decomposition of triethylgallium (TEG) on the substrate surface which has a high density of atomic steps. Growth of multi-layers of GaSb and AlSb on patterned (100) GaSb substrates confirms the results obtained for the planar surfaces by showing the fast growth of the (411)B plane and almost no growth on the (111)B plane. This indicates the possibility for growth of GaSb/AlSb quantum-wire structures.

Growth of GaSb / AlSb heterostructures on patterned substrates by molecular beam epitaxy

InAs / AlSb / GaSb heterostructures with excellent morphological and electrical properties were regrown for the first time on dry-etched GaAs substrates and GaSb epilayers. The shape of the overgrown structures is determined by the adatom species, the crystallographic direction and the growth parameters. For stripe orientations in [011], [001] and [0 1 1] directions, only (111), (110) and (100) planes are formed near the stripe edges. No higher index facets were observed, in contrast to regrowth of GaAs / AlGaAs heterostructures on patterned wafers. Significant differences in growth rates are observed for GaSb and AlSb on (111)A and (111)B facets. On (111)A planes, GaSb and AlSb grow with nearly the same growth rate. However, the growth rate of GaSb on (111)B facets is drastically reduced due to the enhanced migration of Ga from (111)B planes to (100) planes with a higher sticking coefficient for Ga. No degradation of the electrical properties of InAs quantum well structures is observed after regrowth on dry-etched GaSb epilayers, thus proving the suitability of the patterning process.

Growth kinetics of GaSb by metalorganic vapor phase epitaxy

The growth rates of GaSb by metalorganic vapor phase epitaxy were studied as functions of growth temperatures and partial pressures of precursors. A Langmuir-Hinshelwood model was used to explain the GaSb growth rate in the chemical reaction controlled regime. The relationship between growth kinetics and epilayer qualities was discussed and properties of GaSb were obtained.

MOMBE growth of AlSb and AlGaSb using trimethylamine alane

MOMBE (metalorganic molecular beam epitaxy) growth of AlSb and AlGaSb using trimethylamine alane (TMAAl), triethylgallium (TEGa) and solid antimony (Sb 4) is reported for the first time. The growth rate of AlSb shows a monotonic increase with substrate temperature ( T sub) and a decrease with increasing Sb flux. The activation energy for the AlSb growth is 14 kcal/mol at T sub > 460°C and 30 kcal/mol at T sub<460°C. In the AlGaSb growth, the enhancement of the partial growth rate of GaSb is observed and is caused by the TEGa decomposition enhancement effect of the hydrogen atoms from AlH 3. 4.2 K photoluminescence (PL) spectra for the undoped AlGaSb layers exhibit a sharp band-to-band transition with an intensity comparable to that for the GaSb bulk crystal.

Growth of GaSb by MOVPE; Optimization of electrical quality with respect to growth rate, pressure, temperature and [formula omitted] ratio

Factors which affect the very narrow range of optimum IIIV ratios for hetero-epitaxial GaSb on GaAs have been investigated. The GaSb was grown from trimethylgallium (TMGa) and trimethylantimony (TMSb) in a horizontal MOVPE reactor. The growth rate, pressure, temperature, inlet geometry of the cell and/or liner, IIIV ratio and total gas flow rate were investigated with regard to their effect on electrical properties. It was found firstly, that the optimum IIIV ratio varies with reactor pressure. Secondly, the growth rate of GaSb depends on the TMGa concentration, reactor pressure and total flow rate, but not on the TMSb concentration. Finally it was found that the best electrical quality GaSb was obtained with growth rates below 2.5 μm/h irrespective of pressure.