This investigation focuses attention on the very early stages of MBE growth of InSb on GaAs (001). Both conventional and high resolution TEM have been used for a study of InSb layers varying between 5 and 300 monolayers in average thickness. The observations provide conclusive evidence of 3D nucleation and island growth. Complete lattice relaxation is brought about by a network of 1/2 <110> Lomer dislocations at the InSb/GaAs interface and there is strong evidence for the presence of an additional sphalerite interfacial phase. Threading dislocations and planar defects in the InSb epilayer are mainly introduced during island coalescence.

The fabrication of long wavelength opto-electronic devices on GaAs substrates is an attractive method for the monolithic integration of optical and electronic devices on a single chip for applications in telecommunications. InGaAs strained layer quantum wells provide one way of engineering the bandgap needed for 1.3 µm devices at room temperature. We have grown and characterized quantum well structures with bandgap of .96 eV using a novel technique, called spatial strain separation, to avoid the stringent limitation of critical thickness which limits the achievable bandgap in this material system. Moreover we have studied the stability of such structures with respect to thermal processing, including oven and rapid thermal annealing. We have observed no degradation of the quantum wells after thermal annealing as judged from the PL spectra shown here.

InAs chloride ALE has been carried out in detail, resulting in successful InGaAs ALE on (111)B InP substrates. InAs growth of 0.9 ML/cycle is obtained for (111)B InAs substrates at temperatures below 375 °C, while growth rates for (100) and (111)A substrates steadily decrease with increases in growth temperature. The growth rates are independent of InCI pressure at 375 °C, suggesting a self-limiting growth factor in InAs chloride ALE. (GaAs)1(InAs)1 and (GaAs)2(InAs)2 superalloys can be prepared on (111)B InP substrates at 375 °C. Growth rates and crystal compositions for both layers agree well with the values expected for ideal superalloys. The presence of superlattice structures is indicated by X-ray diffraction measurement,

We have grown and characterized heteroepitaxial films of InP on GaAs. We demonstrate that by using flow-rate modulation epitaxy to grow the interface layer in a two-step process, we can improve the quality of heteroepitaxy films. The full-widths-at-half-maximum of the x-ray rocking curve and the 10-K photoluminescence spectrum for a 6.2-μm-thick InP/GaAs are 144 arcsec and 1.28 meV, respectively.

Molecular-beam epitaxy of quantum-well wires on vicinal surfaces is studied by application of Monte Carlo simulations of a solid-on-solid model. Characterization of simulated quantum-well wires indicates an optimum regime within which the quality of the quantum-well wire is maximized. The model is extended to include observed anisotropies in GaAs growth on vicinal surfaces, and the conclusion is reached that better quality quantum-well wires may be grown on substrates misoriented from the (001) towards [110], rather than [110], due to relative step edge stability on the two misoriented surfaces.

Trimethylgallium (TMGa) is an important source gas for metal-organic chemical vapor deposition (MOCVD) and metal-organic molecular beam epitaxy (MOMBE). In the last three years, workers in three different laboratories have examined the pyrolysis of trimethylgallium (TMGa) on heated substrates. However, the mechanism of the decomposition process is still not understood. In this paper we consider the mechanism of the TMGa decomposition on a hot Si(100) substrate in a molecular beam system. It is found that at TMGa doses of 1×1015 molecules/cm2 or less, the decomposition process in the beam system is the same as that reported by Lee et al., Surface Sci. 216, 173 (1989) in studies where TMGa was dosed at low temperature and then the substrate was heated. However, at higher TMGa doses, the mechanism in the molecular beam system is different than the ones reported previously. It is possible to transiently populate a weakly bound state which we assign to TMGa adsorption in the second monolayer. If me sample is below 400 K, the TMGa in the second monolayer desorbs. However, at higher temperatures, the TMGa in the second monolayer can react to form a CHx group (x=3 or 4) and dimethylgallium. The dimethylgallium desorbs. However, some of the CHx groups remain bound to the substrate leading to extra carbon incorporation. There also is evidence for formation of traces of monomethylgallium above 500 K and an indication of methyl radical desorption above 650 K. Thus it seems that at high doses, the decomposition of TMGa on a hot substrate is somewhat different than the decomposition of a monolayer of TMGa which has been adsorbed at low temperatures and then heated. These results explain some of the apparent discrepancies in the literature.

This paper describes an experimental and theoretical study of indium depletion during the OMVPE growth of GaInAs. A mathematical model for mass, momentum and energy transfer, together with decomposition of the indium species was developed. The model was compared with experimental results over a range of growth parameters that included susceptor temperature, slope, reactor pressure and reactant partial pressures. Excellent agreement was obtained for a model based on the homogeneous decomposition of a triethylindium-arsine adduct to a stable product via an irreversible bimolecular reaction, with an activation energy of 11.9 kcal/gmol. The model may be used for optimization of compositional uniformity and growth over a wide range of reactor conditions.

We have grown InP by supplying precursors alternately into the reactor of a metalorganic chemical vapor deposition system. Epitaxial growth has been obtained with a substrate temperature as low as 330 °C. The growth process is mass-transport-limited in the temperature range of 420 to 580 °C. It is kinetic-controlled below 400 °C. At 340 °C, we have achieved monolayer growth in each cycle, i.e., atomic layer epitaxy.

This work reports for the first time, the epitaxial deposition of ln1-xGaxSb on (100)GaAs by Metalorganic Magnetron Sputtering. High quality films could be deposited on GaAs over the entire compositional range despite the large lattice mismatch between the film and substrate (14.6% for InSb and 7.8% for GaSb). The composition of the layers was found to be directly related to the trimethylgallium and trimethylindium fluxes at constant growth temperature. Growth rates of 1 µm/hr for the GaSb and 3 µm/hr for the InSb were observed.

Surface complexes involving Ga and Si adatoms, Si dopant and As vacancies at the GaAs (001) surface are examined for their energetics and associated structural relaxations by employing semi-empirical two- and three-body potential energy functions. The energy minimization is achieved via the simulated annealing Monte carlo procedure. An 8 X 8 X 8 GaAs matrix is used with periodic boundary conditions in the lateral plane. The adatom, dopant or vacancy is added to the system after allowing the top two surface layers to reconstruct into a c (2 × 2) pattern. The suitably chosen neighborhood of the modified site is then allowed to relax to a minimum energy configuration. The complexes are studied for both the unstrained and strained surfaces.

The pulsed laser atom probe has been used to characterise the fine scale chemistry of a range of III-V ternary and quaternary compound semiconductors (GaInAs, AlInAs, GaAlInAs) grown, using MOCVD techniques, on indium phosphide substrates. It has been observed that there are fine scale chemical fluctuations in some specimens on a scale of typically 10–20 nm. The fluctuations appear to be a result of localized clustering of the group III components in the epilayer. In quaternary material there is evidence for different degrees of clustering for different components. It is suggested that this compositional fluctuation is a consequence of clustering occuring above a miscibility gap. The existence of a TEM contrast mechanism inherent to the material has the effect of making TEM an unreliable indicator of fine scale compositional variations in these systems.

Liquid phase electroepitaxial technique has been used for the growth of GaSb and GalnAsSb in the composition range corresponding to peak band gap wavelengths of 1.7-2.28μm. The growth rate of these layers were examined as a function of current density. The growth rates of these layers are typically 0.8μm/min. at a current density of 10A/cm2. The quality of the layers was evaluated by x-ray diffraction and room temperature photoluminescence.

Single crystal layers of gallium arsenide have been grown on <111> and <100> oriented GaAs substrates using a flowing solution of gallium saturated with GaAs. With this novel technique, growth rates as high as 9.Oµm/min have been achieved for 5 minutes, while rates of approximately Aµmlmin are typically achieved for 20 minutes of growth. These figures are in good agreement with a previously developed theoretical model and are about two orders of magnitude greater than those for conventional, static solution, liquid phase epitaxy (LPE) for layer thicknesses greater than lµm. Undoped, p-doped and n-doped layers of high crystallographic and electronic quality have been grown. A description of the technique and some of the electro-optical properties are presented in this paper.

Epitaxial GaAs films have been successfully deposited on three-inch Si wafers with a buried oxide by MOCVD. The SOI wafers were prepared using Separation by IMplantation of OXygen (SIMOX) process. High quality GaAs on SIMOX films, with dislocation density in the range of 2–6 × 106 cm-2, have been achieved using Thermal Cycle Growth (TCG) deposition technique. These films showed a 50-fold increase in the low temperature photoluminescence intensity over conventional deposition. We have also fabricated MESFET’s in GaAs on SIMOX with performance comparable to those fabricated in GaAs. The maximum measured transconductance was in the range of 175-180 ms/mm at a 1.5 µm gate length and a 5 µm source to drain separation. This is the first demonstration of large area, high quality and low defect density GaAs on SIMOX.

High quality (100) single domain GaAs layers are epitaxially grown on slightly misoriented (100) Si-on-(1102) sapphire(SOS) substrates by MOCVD. Epitaxial growth on a spherical SOS substrate reveals that R face (1102) should not be tilted toward C axis [0001], but toward [011] or [011] of Si. A new MOCVD system which has two reactors, one for Si cleaning, the other for GaAs deposition, is effective to obtain mirrorlike smooth surface. The X-ray FWHM of 10µm GaAs was reduced to 65 arcsec by the thermal cycle annealing.

A crack free 15 µm thick GaAs layer with a dislocation density of 3×106cm-2 is obtained by combining the thermal cycle annealing and the strained-layer superlattices.

White beam synchrotron topography in both transmission and grazing Bragg-Laue geometries has been used to reveal the 3-dimensional defect structure in MBE grown GaAs epilayers on Si. Defects observed and characterized include substrate threading dislocations and interfacial dislocations. Dislocation line direction and Burgers vector analysis was performed on transmission topographs. The relationship between substrate threading dislocations and interfacial dislocations was established. In the grazing Bragg-Laue case, manipulation of geometry enabled depth profiling of defect structures in the epilayer. The position of the interfacial dislocations was verified by correlating penetration depth analysis with the visibility of the dislocations under different diffraction conditions.

This technique affords a rapid and non-destructive way of quantitatively characterizing processing induced damage in such systems.

In this work, activation of Si implanted into GaAs-on-Si layers grown by molecular beam epitaxy (MBE) is studied. We have found that activation efficiency of implanted Si is lower in GaAs on Si than in bulk GaAs and varies widely. By studying the activation of non-amphoteric dopants such as Be and S, we have found that no donor- or acceptor-like defects exist in high concentrations in GaAs on Si and that amphoteric behavior of Si is the major compensation mechanism in MBE-grown GaAs on Si. Increased Si-acceptor concentration and S activation in GaAs on Si are apparently due to a high density of As vacancies which result from a low V(As):III(Ga) flux ratio during growth. The effect of the threading dislocations does not appear to be significant compared to that of As vacancies as no correlation is found between the density of threading dislocations and implanted Si activation.

Deep level transient spectroscopy (DLTS), current-voltage- temperature (I-V-T), capacitance-voltage-temperature (C-V-T), C-T and photoreflectance spectroscopy (PRS) were used to compare the electrical properties of GaAs p-n junctions epitaxially grown by MOCVD on GaAs and Si substrates. EL2 was detected for both GaAs/GaAs and GaAs/Si structures. For GaAs/Si, a continuous distribution of trap levels was also observed which could be ascribed to misfit defects. I-V-T data revealed the saturation current of GaAs/Si diodes to be four orders in amplitude higher than for GaAs/GaAs ones. Different temperature dependences were found in saturation current density, barrier height and capacitance between the two structures. A multistep tunneling model is utilized in explaining the results for GaAs/Si. C-T measurements indicated the free carriers not to be frozen-out for GaAs/Si at the freeze-out temperature of GaAs/GaAs. A defect- induced bandgap tailing effect might be responsible for this effect, verified by PRS tests.

Successful selective area growth of GaAs on Si following low-temperature plasma cleaning of the Si surface is carried out by ECR plasma-excited MBE. Both cleaning and selective area growth are carried out at 630° C. GaAs selectively grows only in Si windows patterned in the SiN mask. Neither deposition on the SiN mask nor anomalous growth at the mask edge is observed. GaAs thickness is independent of the SiN mask width, which implies that the plasma-enhanced desorption of migrating atoms from the SiN mask is essential in this selective area growth. Furthermore, results for the helium-diluted arsine imply that the plasma-enhanced desorption is mainly caused by physical bombardment.

GaAs layers were deposited onto Si(100) substrates using molecular beam epitaxy (MBE). The substrates were prepared by various methods before the growth of 0.1µm thick GaAs buffer layers. Active GaAs layers were thereafter grown with thicknesses from 1 to 4µm. Infrared spectra were recorded in the spectral ranges from 12 to 65cm-4 and 50 to 500cm-1 of the thin buffer layers as well as the thick active layers. The infrared active phonon of GaAs already shows up in the spectra for the 0.1µm buffer layers. The phonon parameters were derived from a harmonic oscillator fit to the experimental data. The phonon damping constant is correlated with the bulk quality of the GaAs layers. These results are compared with those obtained from Raman and spectroscopic ellipsometry measurements.