T. D. Golding

Raman spectroscopy of InSb/CdTe heterostructures: Improved interface quality obtained by Cd overpressure during molecular beam epitaxial growth

In recent photoemission and Raman experiments interfacial layers of indium telluride together with liberated antimony were found to be formed during the molecular beam epitaxial growth of CdTe on InSb(100) at elevated substrate temperatures (TS≥200 °C). We have previously suggested that the application of a sufficiently large Cd overpressure during growth is likely to suppress the formation of interfacial layers and enable successful epitaxial growth of CdTe. In this letter we present Raman spectra revealing that a flux ratio of Cd/Te=3 during growth effectively suppresses indium telluride formation leading to largely improved InSb/CdTe interfaces.

Investigation of Sb/GaSb multilayer structures for potential application as an indirect narrow-bandgap material

In this paper the authors provide the rationale, and a preliminary experimental investigation of, the Sb/GaSb system as a potential indirect narrow-gap superlattice, where spatial quantization effects are proposed to induce a positive valence-conduction band energy gap in the Sb semimetal layers. The experimental study has investigated growth of Sb/GaSb single heterojunctions and elementary multilayer structures using molecular beam epitaxy. Although Sb is rhombohedral and GaSb has the cubic zinc blende structure, the biatomic planar structure of Sb mimics the (111) plane in the zinc blende structure, and registry between the zinc blende and rhombohedral lattice can be preserved if epitaxy is achieved along the (111) direction. The authors show that high-quality Sb layers can be grown epitaxially on GaSb(111) homoepitaxial films, and that GaSb can be subsequently grown on Sb. The epilayer growth and heterojunction structure have been characterized by in situ reflection high-energy electron diffraction, X-ray diffraction and X-ray photoelectron spectroscopy. Electrical properties of Sb epilayers with thicknesses in the range 150-2500 AA have been determined by temperature-dependent Hall measurements.

Epitaxial and interface properties of InAs/InGaSb multilayered structures

We have used the technique of molecular beam epitaxy to grow InAs on GaSb, GaSb on InAs, and InAs/InxGa1−xSb (0≤x≤0.4) multilayered structures and have performed a detailed investigation of the layers and resultant interfaces. The structures were grown on (100) oriented GaSb or GaAs substrates. Combined reflection high energy electron diffraction, x‐ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) studies indicate that Sb is persistently present on the InAs growth surface. XPS and AES analysis of InAs/GaSb heterojunctions indicates no compound formation at either the InAs/GaSb or GaSb/InAs interface. Secondary ion mass spectroscopy (SIMS) and XPS extinction profiles reveal the presence of approximately 5–10% As in the nominally pure GaSb layers. Analysis of InAs/GaSb/GaSb (100) structures by SIMS indicates that the As is incorporated during growth. The multilayer structures have been characterized by double crystal x‐ray diffraction and the data has been modeled using kinematic ...

Epitaxial growth of Sb/GaSb structures: An example of V/III‐V heteroepitaxy

The requirements for heteroepitaxial growth of Sb on both GaSb and GaAs, and the subsequent growth of GaSb on Sb, using molecular‐beam epitaxy are described. These systems serve as examples of the heteroepitaxy of group‐V elements with III‐V compounds, i.e., between materials utilizing different bonding and possessing different electronic properties. The quality of the films was determined using high‐resolution four‐circle x‐ray diffraction, and comparisons were made between different structures. GaSb was found to grow (111) oriented on Sb (111) with an inverted stacking sequence. A simple epitaxial model is proposed to explain this.

Molecular Beam Epitaxy Study of InAs/GaSb Heteroepitaxy on The (111)A and (111)B Orientations

We have investigated the molecular beam epitaxial growth of homoepitaxial InAs and GaSb and InAs/GaSb heterostructures on both the (111)A and (111)B orientations. Our studies have found that high quality GaSb epilayers can be grown on both the (111)A and (111l)B orientations over a wide range of growth temperatures and flux ratios. Reflection high energy electron diffr-action phase diagrams for GaSb [111[ are presented. InAs/GaSb heterostructures, simultaneously grown on (11l)A and (111)B orientations, have been investigated by secondary ion mass spectroscopy depth profiles and double crystal x-ray diffraction. Unintentional incorporation of the ‘second’ group-V element is found to be approximately three times greater in the (111)A orientation than in the (111)B for both species.

An ellipsometric method for the determination of the dielectric tensor of an optically uniaxial material suited for in-situ measurements

We introduce a photometric ellipsometric method to determine the dielectric tensor of an optically uniaxial material suited for in-situ measurements. The technique employs a rotatable polarizer to provide a series of polarization states, eliminating the need for sample rotation or changes in angle of incidence. A method is presented that enables extraction of the dielectric tensor using standard rotating analyzer methods. As an example, the method is used to determine the indices of refraction and the orientation of principal axes for a calcite crystal.

Reflection high‐energy electron diffraction study of growth and interface formation of the Ga1−xInxSb/InAs strained‐layer superlattices

Growth and interface formation of the Ga1−xInxSb/InAs (x≤0.4) strained‐layer superlattices (SLSs) on GaSb(100) substrates have been studied by the reflection high‐energy electron diffraction (RHEED) during molecular beam epitaxy. A number of surface atomic structures were observed in the growth of the SLS: a (1×3) phases from the InAs epilayer surface; a (2×3) phase, a (2×4) phase and diffuse (1×1)‐like phases from the InAs epilayer surface. The RHEED intensity variations in the formation of the interfaces have been discussed in terms of interface chemical reactions.

HIGH-RESOLUTION X-RAY DIFFRACTION STUDY OF IN0.25GA0.75SB/INAS SUPERLATTICE

An In 0.25 Ga 0.75 Sb/InAs strained-layer superlattice, grown by molecular-beam epitaxy (MBE) on a GaSb[001] substrate, has been characterized by four-circle x-ray diffractometry. This system, proposed by Maliot and Smith for ir detection application, is challenging because of the two group V species and the likelihood of cross-incorporation of the different elements during growth, leading possibly to interdiffusion and thus, to a more diffuse interface. High-resolution x-ray diffraction (XRD) profiles were obtained about several reciprocal lattice points in order to extract a reliable set of structural parameters. The profiles were then successfully modeled by computer simulation. The presence of many sharp higher-order satellite reflections in the XRD profiles is a measure of the high quality of the superlattices. The normal and lateral structural coherence was also measured and will be discussed.

Molecular beam epitaxial growth of Sb/GaSb multilayer structures: potential application as a narrow bandgap system

Abstract We have performed an investigation into the synthesis of Sb/GaSb heterojunctions and multilayered structures grown by molecular beam epitaxy. The study has been motivated by the potential of the system as an indirect narrow-gap superlattice, where spacial quantization effects are proposed to induce a positive valence-conduction band energy gap in the Sb semimetal layers, and the potential to exploit the large characteristic lengths in the Sb layers for the study of size quantization effects. The GaSb/Sb system presents a number of unique features with regard to synthesis of the epitaxial semimetal/semiconductor system. On the (111) plane of the rhombohedral crystal structure of Sb, both the hexagonal symmetry and in-plane lattice parameter allow near perfect registry to the Sb atoms on the (111) plane of the zincblende structure of GaSb. We show that Sb can be grown epitaxially on GaSb on both (111)A and (111)B orientations for growth temperature T s C and that GaSb can subsequently be grown on the Sb epilayers. The successful growth of GaSb at temperatures less than 240°C has been achieved using migration enhanced epitaxy. Epilayer growth of Sb and Sb/GaSb heterojunction structures have been characterized by in situ reflection high energy electron diffraction, X-ray diffraction and X-ray photoelectron spectroscopy.

Sb/GaSb heterostructures and multilayers

We have successfully synthesized heterojunctions and elementary multilayered structures of the semimetal‐semiconductor system Sb/GaSb using molecular beam and migration enhanced epitaxies. The study is motivated in part by the potential for producing an indirect narrow‐gap semiconductor, in which a confinement‐induced positive energy gap in the Sb layers will lead to highly attractive properties for nonlinear optical switches operating in the infrared. One may also be able to exploit the long mean free path in Sb (up to 2 μm) in studying quantum transport phenomena. X‐ray diffraction confirms the ordered growth of GaSb/Sb/GaSb multilayers, and field‐dependent magnetotransport measurements yield electron and hole mobilities ≥3×104 cm2/V s in Sb thin films.