xSbx Layers Research Articles

Moving photoluminescence bands in GaAs1−xSbx layers grown by molecular beam epitaxy on InP substrates

We report the excitation intensity dependent photoluminescence properties of GaAs1−xSbx layers grown by molecular beam epitaxy on InP substrates. Photoluminescence consists of the bound exciton and the quasi-donor-acceptor pair transitions for the layers in the range of 0.26≤x≤0.94. The concentration modulation produced by the relaxation of the misfit strain between the epitaxial GaAs1−xSbx layer and InP substrate is responsible for the quasi-donor-acceptor pair transition. A large Stokes shift between the photoluminescence transition of the bound exciton and the band gap determined by the optical absorption measurements is also consistent with our model of concentration modulation.

Bi1−xSbx/Bi superlattice grown by molecular beam epitaxy

Superlattices of Bi1−xSbx/Bi have been grown by molecular beam epitaxy on CdTe(111) substrates. The typical multilayer, consisting of Bi1−xSbx (85 Å with x=0.16) and Bi (75-Å) layers repeated 50 times, was grown at a substrate temperature of 150 °C. The samples were characterized by reflection high-energy electron diffraction (RHEED), θ-2θ x-ray diffraction analysis, and high-resolution transmission electron microscopy. The streaked RHEED patterns with clear Kikuchi lines and the x-ray satellite peaks indicate a good epitaxial layer quality. The bright field transmission electron microscopy image of the superlattice film confirms that a composition modulation exists, even though the Bi1−xSbx and Bi layers have only a slight image contrast.

Optical absorption and emission of InP1−xSbx alloys

A detailed optical study of the metastable III/V semiconductor alloy InP1−xSbx is presented. InP1−xSbx layers are grown throughout the entire compositional range by atmospheric pressure organometallic vapor phase epitaxy on InP, InAs, and InSb substrates. Composition and strain are measured by combined electron microprobe analysis and x-ray diffractometry. The dependence of band gap on composition is experimentally established for the first time from absorption spectra measured at 10 and 300 K. The resultant value of the band-gap bowing parameter is 1.52±0.08 eV, independent of temperature. The absorption spectra show the InP1−xSbx layers to have long band tails, which extend further into the gap as the Sb concentration is increased. The band tails are induced by compositional clustering. Photoluminescence (PL) spectra are measured between 10 and 300 K. The PL peaks are assigned to recombination between carriers occupying band-tail states or to recombination via deep centers in the gap.

Growth and optical characterization of InAs1−xSbx(0≤x≤1) on GaAs and on GaAs-coated Si by molecular beam epitaxy

Epitaxial layers of InAs1−xSbx(0≤x≤1) have been grown on GaAs and on GaAs-coated Si substrates by molecular beam epitaxy using tetrameric Sb and dimeric As sources. Room-temperature transmission spectroscopy was used to measure the optical band gap of the InAs1−xSbx layers and the composition was determined by x-ray wavelength dispersive spectroscopy. We obtained shiny morphology InAs1−xSbx layers on GaAs-coated Si, comparable to those grown on GaAs. Our results are very encouraging towards the monolithic integration of InAs1−xSbx long-wavelength infrared detectors with Si charge-coupled devices.

Growth of InSb and InAs1−xSbx on GaAs by molecular beam epitaxy

InSb and InAs1−xSbx epitaxial layers have been successfully grown on (100)GaAs substrates by molecular beam epitaxy. Remarkably good morphologies were obtained despite the large lattice mismatch (14%) between InSb and GaAs. Room-temperature electron mobilities as high as 57 000 cm2/V s were measured in InSb layers of about 5 μm thick with ND−NA∼1.6×1016 cm−3. The substrate temperature and Sb/In flux ratio were found to critically influence the quality of InSb epilayers. By employing dimeric instead of tetrameric sources, the composition of the InAs1−xSbx films was observed to be relatively independent of substrate temperature. Electron mobilities of 20 000 and 8800 cm2/V s, at 300 and 77 K, respectively, were obtained for a 1.6-μm-thick InAs1−xSbx (x=0.67) layer.

Ordered structures in GaAs0.5Sb0.5 alloys grown by organometallic vapor phase epitaxy

Electron diffraction measurements on (100) GaAs1−xSbx layers with x≊0.5 grown by organometallic vapor phase epitaxy indicate that ordered phases are formed during growth. Two ordered phases are observed. The simple, tetragonal AuCu-I type phase consists of alternating {100} oriented GaAs and GaSb layers. Only the two variants with the tetragonal c axes perpendicular to the growth direction are observed. At least two variants are observed for the chalcopyrite E11 structure with alternating {210} oriented GaAs and GaSb layers.

Reflectivity spectra of epitaxial GaAs-rich GaAs1−xSbx

Epitaxial single-crystalline GaAs-rich GaAs1−xSbx layers have been examined at room and liquid nitrogen temperatures by means of reflectivity measurements in the fundamental absorption region. The energies of observed interband transitions have been linearly correlated with the composition.

Reduction of the Dislocation Density in GaAs1 − xSbx Layer on GaAs Grown by an Improved LPE Method

An improved LPE method in which the solid surface is always covered by a solution during step‐graded growth of on substrates produces etch pit densities of . In contrast, layers grown by conventional step or continuously graded LPE have EPD of . The composition of the top layer is approximately in all cases. The reduction of EPD by the improved LPE method is attributed to limiting the nucleation of small islands to the first buffer layer, under the conditions that the grown surface is always covered by the solution subsequent to the growth of the first buffer layer.

Silicon-doped gallium arsenide antimonide electroluminescent diodes emitting to 1.06 μm

We report efficient room-temperature emission to 1.06 μm from silicon-doped gallium arsenide antimonide electroluminescent diodes fabricated in GaAs1−xSbx layers grown on GaAs substrates in a single-step LPE growth from melts containing from 0.1 to 1.1 at.% Si. The spectral half-width of the emission is 42.5 nm at 0.96 μm and 79 nm at 1.06 μm.