GaSb Monolayers Research Articles

Many-body perturbation theory study of type-II InAs/GaSb superlattices within the GW approximation

Recent studies suggest that the many-body perturbation theory in the partially self-consistent GW (GW0) approximation significantly improves the prediction of band gaps in various semiconductors. In this work, we employed GW formalism to study the electronic structure of type-II InAs/GaSb strained-layer superlattices (T2SLs). T2SLs considered in this study, denoted by (monolayers of InAs, monolayers of GaSb) are (), (), (), (), and (). The InSb-type interfacial layer was introduced in the structures to resemble the actual growth condition in our laboratories. The electronic band gaps are indirect in all the structures. The band gaps at the center of the Brillouin zone show good agreement with experimental data. This study is the first step to investigate the electronic, optical, and defect characteristics of T2SLs within a parameter-free ab initio method.

Molecular Beam Epitaxy of Zero Lattice-Mismatch InAs/GaSb Type-II Superlattice**Supported by the National Basic Research Program of China under Grant Nos 2015CB351902, 2015CB932402 and 2012CB619203, the National Natural Science Foundation of China under Grant Nos 61177070, 11374295 and U1431231, and the National Key Research Program of China under Grant No 2011ZX01015-001.

Type-II InAs/GaSb superlattices made of 13 InAs monolayers (MLs) and 7 GaSb MLs are grown on GaSb substrates by solid source molecular beam epitaxy. To obtain lattice-matched structures, thin InSb layers are inserted between InAs and GaSb layers. We complete a series of experiments to investigate the influence of the InSb deposition time, V/III beam-equivalent pressure ratio and interruption time between each layer, and then characterize the superlattice (SL) structures with high-resolution x-ray diffraction and atomic force microscopy. The optimized growth parameters are applied to grow the 100-period SL structure, resulting in the full-width half-maximum of 29.55 arcsec for the first SL satellite peak and zero lattice-mismatch between the zero-order SL peak and the GaSb substrate peak.

Device quality Sb-based compound semiconductor surface: A comparative study of chemical cleaning

We have studied the surface cleaning of Sb-based compound semiconductors using HF, NH4OH, and HCl cleans and the metal–oxide–semiconductor (MOS) capacitors fabricated subsequently. GaSb, InGaSb, and AlGaSb surfaces are investigated using low-energy radiation from the synchrotron. Capacitance–voltage (C–V) and photoluminescence measurements are carried out on capacitors made with Al2O3 from atomic layer deposition and corroborated with the results from synchrotron spectroscopy. Excellent C–V characteristics with a mid-band-gap interface state density of 3 × 1011/cm2eV are obtained on samples with the HCl clean. This is consistent with the finding that only the HCl acid clean is able to remove the native oxides present on GaSb and InGaSb surfaces, and produce clean and stable surfaces suitable for MOSFET development. Complete removal of AlOx on the AlGaSb surface was not possible using chemical cleaning. Termination of AlGaSb with two monolayers of GaSb is proposed as a solution.

Noise Characterization of Midwave Infrared InAs/GaSb Superlattice pin Photodiode

We report on noise characterization of a midwave infrared (MWIR) InAs/GaSb superlattice (SL) single detector. The SL structure was made of eight InAs monolayers (MLs) and eight GaSb MLs, with a total thickness of 2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> (440 SL periods). This structure exhibits a cut-off wavelength of 4.8 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> at 77 K. Extracted from current–voltage characteristics, zero-bias resistance area product <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${R} _{0}{A}$</tex> </formula> above <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$5\times 10 ^{5} ~\Omega \cdot \hbox{cm}^{2}$</tex></formula> at 80 K was measured. Noise measurements were also performed under dark conditions. The measurements reveal the absence of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ 1/{f}$</tex></formula> noise above 30 Hz. Moreover, the detector under test remains Schottky noise-limited up to a bias voltage of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-$</tex></formula> 200 mV typically, which confirms the quality of the MWIR SL pin photodiode.

Interface analysis of InAs/GaSb superlattice grown by MBE

We report on the structural characterization of short period type-II InAs/GaSb superlattices (SLs) adapted for mid-infrared detection. These structures, grown by molecular beam epitaxy (MBE) on n-type GaSb substrates, are made up of 10 InAs monolayers (MLs) and 10 GaSb MLs and a strain balanced condition is obtained by inserting an InSb ML at the interface between InAs and GaSb in each superlattice's period. From cross-sectional transmission electron microscopy (TEM) measurements, the interface structure is analysed in detail. Very homogeneous and smooth InAs and GaSb layers all over a 50 periods SL structure are observed and high-resolution images bring out the InSb ML inserted between InAs and GaSb. Room temperature absorbance spectroscopy measurements have been performed on strain-compensated SLs including 50, 100, 300 and 400 periods, for a total absorption zone thickness of 0.32, 0.64, 1.92 and 2.56 μm, respectively. The spectra display reproducible and well-defined features with an absorption coefficient varying between 2×10 3 and 4×10 3 cm −1 in the 3–5 μm mid-infrared domain, a sign of high-quality samples suitable for detection.

Optical characterization of symmetric InAs/GaSb superlattices for detection in the 3–5 μm spectral region

Type-II InAs ( N )/GaSb ( N ) superlattices (SLs) where the SL's period is composed by equal number N of InAs and GaSb monolayers (MLs) have been grown by solid source molecular beam epitaxy on n-type GaSb substrate. These SLs are made up of 100 periods with a number of MLs varying from N = 5 to 15. Photoluminescence and photoresponse measurements, performed at 80 K, displayed peak positions and cut-off wavelengths between 3.8 and 8.3 μm. These results are in good agreement with a modified envelope function approximation model taking into account a strong perturbative potential at each InAs/GaSb interface. P-i-n photodetectors, made-up from strain-compensated InAs (10)/GaSb (10) undoped superlattice, showed a cut-off wavelength at 5.6 μm, an absorption coefficient value varying from 4×10 3 to 5.5×10 3 cm −1 in the 3–5 μm wavelength range, and a photovoltaic response up to 260 K.

MBE growth and characterization of type-II InAs/GaSb superlattices for mid-infrared detection

Type-II InAs/GaSb superlattices (SLs) made of 10 InAs monolayers (MLs) and 10 GaSb MLs, designed to have a cut-off wavelength of 5.4 μm, have been grown on GaSb substrates by solid source molecular beam epitaxy (MBE). In order to obtain lattice-matched structures, a thin layer of InSb was inserted at the GaSb on InAs interface. We demonstrate that structural and optical properties of such structures strongly depend on the thickness of the InSb inserted layer. Strain-balanced InAs/GaSb SLs could be grown, after optimizing the MBE shutter sequence, by using a growth temperature of 390 °C and an inserted InSb layer of thickness 1 ML. Non-optimized pin diodes using 100 periods of such an SL as absorbing material showed an absorption coefficient varying from 4×10 3 to 6×10 3 cm −1 at room temperature in the 3–5 μm mid-infrared wavelength region, and a photovoltaic response up to 230 K.

The effect of interface bond type on the structural and optical properties of GaSb/InAs superlattices

The effect of interface bond configuration on the structural and optical properties of short-period ( approximately=50 AA) GaSb/InAs superlattices has been examined. Structures consisting of eight monolayers of GaSb and seven monolayers of InAs with either 'GaAs-like' or 'InSb-like' interface bonds were grown by MBE. Evidence for differences in the structural properties, vibrational properties and band structure of the two types of material was obtained using X-ray diffraction, Raman scattering, interband magneto-absorption and photoconductivity measurements.