GaAs-Si Interface Research Articles

Heteroepitaxy for GaAs on Nanopatterned Si (001)

An almost defect pit-free GaAs is achieved using nanopatterned Si (001). The largest nanopattern with an aspect ratio of 4.18 and the narrowest strip of around 55 nm in width are adopted in this letter. The threading dislocations, beginning from the GaAs-Si interface and moving along the facet plane to the sidewall, are interrupted within the initial epitaxial layer. With the aspect ratio increasing from 0.44 to 2.04, the etching defect pit density can be decreased from around 5.0 × 109 cm-2 to almost zero. The improvement in material quality is verified by transmission electron microscopy, photoluminescence, and X-ray diffraction studies.

Properties of the GaAs–Si Interface in Epitaxy through an Aluminum Layer

The interaction of elements near the interface during epitaxial growth of monocrystalline GaAs films through an aluminum layer is investigated by the methods of x-ray photoelectronic spectroscopy and secondary-ion mass spectroscopy.

Improvement of Microwave Performance for Metal-Semiconductor Field Effect Transistors Fabricated on a GaAs/Si Substrate with a Resistive Layer at GaAs–Si Interface

We report on the improvement in the microwave performance of metal-semiconductor field effect transistors (MESFETs) fabricated on GaAs/Si with a resistive layer at the GaAs-Si interface. This layer was obtained by using a p-type AlGaAs layer or an oxygen-doped AlGaAs layer grown by metal-organic chemical vapor deposition (MOCVD). Correlation between sheet carrier concentration in the resistive layer and the device performance was studied and a marked improvement was found by reducing the number of carriers in the layer to 4.1×1012 cm-2, which was about 1/5 of that for standard GaAs/Si. High cutoff frequency of 22 GHz, comparable to that of MESFETs/GaAs, was obtained for 0.8-µm-gate-length MESFETs/Si with a sheet carrier concentration of 1.5×1012 cm-2. On evaluating scattering parameters for improved MESFETs/Si, it was found that the parasitic pad capacitance, characteristic for standard GaAs/Si, became as small as that for MESFETs/GaAs. These results demonstrate that GaAs/Si with a resistive layer is applicable to GaAs electronic devices.

Measurement of Carrier Concentration at the GaAs–Si Interface in GaAs on Si by Raman Scattering

The free carrier concentration in GaAs-on-Si was measured by Raman scattering at the GaAs back face which is revealed by etching the Si substrate. Asymmetric Raman spectra attributed to the coupled plasmon-longitudinal optical (LO) phonon mode ( L+) observed in the range of 400 to 700 cm-1 indicate that an electron concentration greater than 1.6×1018 cm-3 is induced by incorporation of Si atoms into the GaAs layer at the Si–GaAs interface in metal-organic chemical vapor deposition (MOCVD) grown GaAs-on-Si's at 700° C for 15 min.

TEM study of the structure of GaAs on vicinal Si (001) surface grown by MBE

Molecular beam epitaxy (MBE) grown GaAs films on Si substrates (0 0 1) 4° off towards 〈1 1 1〉 A and towards 〈1 1 1〉 B, were examined by means of transmission electron microscopy (TEM). The results indicate that in both samples, threading dislocations in the GaAs epilayer are blocked mainly in a thin layer near the GaAs-Si interface. This thin layer is like an inner interface, consisting of pyramidal islands and is flatter on the As growth surface than that on the Ga growth surface. In the type B sample, the density of dislocations is lower, the inner interface is flatter and the number of twins is much larger than that in the type A sample.

Characterization of GaAs thin films grown by molecular beam epitaxy on Si-on-insulator

The direct growth of GaAs by molecular-beam epitaxy (MBE) on silicon-on-insulator (SOI) structure is presented. Rutherford backscattering and channeling (RBS/C), transmission electron microscope (TEM), and infrared (IR) reflection measurements have been employed to characterize the GaAs thin films. RBS/C results show that there is considerable lattice disorder at the GaAs-Si interface, but the crystal quality of the GaAs thin films improves remarkably toward GaAs surface for thicker films where the minimum channeling yield drops to 10% IR reflection spectra in the wavenumber range 1500 - 5000 cm-1 were measured for GaAs thin films on SOI. Interference fringes observed in IR reflection spectra also prove that the crystalline GaAs thin films have been deposited on SOI substrates. By computer simulation of the IR reflection interference spectra refractive index profiles of the GaAs/SOI structures were obtained.

A STUDY OF ELECTRONIC CHARACTERIZATION IN MOLECULAR BEAM EPITAXIALLY GROWN GaAs ON Si

The electronic characteristics of GaAs grown on Si by molecular beam epitaxy(MBE) has been examined by studying the diode characteristics and deep level transient spectroscopy (DLTS) of Schottky barriers. l-V characteristics of samples show the existence large leakage current. Post-growth rapid thermal annealing(RTA)has been found to be able to significantly improve the diode behaviour. The reverse current in the as-grown material shows a very weak temperature dependence, indicating that its origin is not thermoionic emission or generation-recombination currents. We think that a large part of this current is due to defect-assisted tunneling, which is reduced by RTA. DLTS spectra show that Ec-0.41eV and Ec-0.57eV electron traps are observable. The former is located near the GaAs-Si interface probably, the latter relates to the well-known electron trap M5 typical of MBE GaAs.

Modulated reflectance study of strain in epitaxial GaAs on silicon

The electrolyte electroreflectance technique was used to study the nature of the strain in epitaxial layers of GaAs grown by laser-assisted metalorganic chemical vapor deposition on (100) Si substrate. The GaAs epilayer, about 140 nm thick, was chemically etched in steps of about 20 nm and spectra of the differential reflectivity (ΔR/R) versus energy were recorded in the 2.4–4.0 eV region immediately following each etch procedure. The E1 and E1+Δ1 transitions of GaAs and their broadening parameters were calculated using the low-field analysis of the electrolyte electroreflectance line shapes. The uniformity of carriers and the effects of the etching procedure were studied with three-dimensional amplitude maps. The variations of the spectral characteristics are interpreted in terms of strains and electronic changes as one approaches the GaAs-Si interface.

Antiphase Defect Reduction Mechanism in Mbe Grown Gaas on Si

ABSTRACTIt is shown that antiphase boundary (APB) is annihilated during the growth, by monitoring the surface with reflection high energy electron diffraction (RHEED). The RHEED observation indicates that double domain GaAs changes to single domain within a thickness of 100 nm, while the transition region is estimated to exist within 200 nm from GaAs-Si interface by scanning electron microscope (SEM) observation of etch pits on vicinally polished surface. The self-annihilation mechanism of APB is discussed from these results.

Omvpe Growth and Characterization of GaAs on Si for Device Applications

AbstractSignificant progress has been made in the OMVPE growth of GaAs directly on Si by the previously reported low-temperature growth technique. These films have been characterized by low-temperature PL, SIMS, TEM, and DLTS. The epitaxial layers, whose quality has been determined by PL measurements (4.2 K PL spectral width of heavy-hole exciton ≈ 3 meV), were implanted with 29Si+ for fabrication of MESFET channels. Background concentrations of ≈ 1014 cm−3 have been achieved for the first time after rapid thermal annealing without the need to use oxygen implantation or vanadium doping. SIMS measurements do not show Si pileup on the surface or much Si diffusion at the GaAs-Si interface, a significant improvement over earlier results. DLTS measurements and electrical characterization of the GaAs-Si heterojunction diode indicate the presence of only two trap levels (< 1014 cm−3 in concentration) in the GaAs ≥ 2.5 μm away from the interface.

Control of dislocations in GaAs grown on Si(211) by molecular beam epitaxy

The dislocation arrangements in GaAs films grown on Si substrates with (211) surface orientations were directly determined using transmission-electron microscopy in planar and cross-sectional views. The dislocations consisted of high density networks at the GaAs–Si interface and arrays of linear dislocations that propagated from the interface to the surface of the film on the (11̄1̄) planes. Burger’s vector determination of the arrays indicated that dislocations are introduced into the film primarily by a glide process and that the linear arrays are a remnant of the interface network. When strained layer InxGa1−xAs/GaAs superlattices were used, the linear arrays were observed to form a closed dislocation network, with the top of the loop structure coincident with the top of the superlattice. The dislocation density was markedly reduced above the superlattice. Our results indicate that careful control of the strain can be an effective means of altering dislocation distributions in the films.

Activation characteristics and defect structure in Si-implanted GaAs-on-Si

Undoped metalorganic chemical vapor deposited GaAs layers on Si substrates were implanted with 29Si ions (5×1012 cm−2 dose at 100 keV energy) to form a shallow n-type region. The net donor activation (74%) and electron mobility (3014 cm2 V−1 s−1) after rapid thermal annealing (900 °C, 10 s) were compared to those obtained for similar implants into bulk GaAs. There was a slight improvement in the proton backscattering yield from the GaAs-Si interface region after the annealing cycle, consistent with cross-sectional transmission electron microscopy data showing an alignment of defects in annealed samples.

MBE Growth of GaAs on Si (100)

ABSTRACTMolecular beam epitaxy (MBE) growth of GaAs on Si was investigated for three Si substrate orientations: exact (100), 4° off (100) towards (011), and 4° off towards (010). Cross-sectional transmission electron microscopy (X-TEM) analysis indicated a high dislocation density at the GaAs-Si interface that decreased away from the interface. Changing the orientation significantly affected the dislocation arrangement in the films.In the exact (100) case, dislocations from different glide systems formed pyramids, and dislocation annihilation resulted in linear defects propagating to the bottom of pits on the GaAs surface. On Si substrates oriented 4° off of (100), dislocation pyramids were not observed which we attribute to the different stresses acting on different glide systems. Planar TEM sections indicated that the dislocation densities at th surfaces of the 2-μm-thick films were 8 × 108 /cm2 for exact (100), 3.4 × 108/cm2 for 4° off (100) towards (010), and 1.6 × 108/cm2 for 4° off towards (011) orientations. When etching was used to evaluate anti-phase domain (APD) density, the exact (100) and off (100) orientations toward (010) showed APD's in some areas; off (100) toward (011) orientations were apparently APD-free. Results of photoluminescence (PL) spectroscopy of each of the wafers showed marked differences in peak intensities for the different orientations. Secondary ion mass spectrometry (SIMS) showed that roughly 1/4 of a monolayer of Si was incorporated in the GaAs, mostly concentrated in the first 250 nm near the GaAs-Si interface.