Optoelectronic properties of InAs/GaSb superlattices with asymmetric interfaces (original) (raw)
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Theory of optical properties of segregated InAs/GaSb superlattices
Iee Proceedings-optoelectronics, 2003
The authors study the effects of interfacial atomic segregation on the electronic and optical properties of InAs/GaSb superlattices. They describe their atomistic empirical pseudopotential method and test its performance against the available experimental data. They show its ability to predict the band structure dependence on the detailed atomic configuration, and thus to properly account for the effects of interfacial atomic segregation and structural disorder. They also show how their method avoids the approximations underlying the pseudopotential method of Dente and Tilton, which gives different results. The application of the proposed method to the InAs/GaSb superlattices allows the explanation of some observed experimental results, such as: the bandgap difference between ðInAsÞ 8 =ðGaSbÞ 8 superlattices with almost pure InSb-like or GaAs-like interfaces; the large blue shift of the bandgap when the growth temperature of the superlattice increases; and the blue shift of the bandgap of ðInAsÞ 8 =ðGaSbÞ n superlattices with increasing GaSb period n. They present a detailed comparison of their predicted blue shift with that obtained by other theories.
Optical and structural characterization of InAs/GaSb superlattices
Journal of Applied Physics, 1997
InAs/GaSb superlattices sandwiched between conventional InAs layers were grown by low pressure metal organic chemical vapor deposition. Period and roughness of the superlattices were examined by field emission transmission electron microscopy. Room temperature infrared absorption spectra for InAs/GaSb superlattices were obtained by Fourier-transform infrared spectroscopy. The effects of varying the doping levels and thicknesses of the InAs sandwiching layers on the absorption spectra of InAs/GaSb superlattices were studied. It was found that by choice of suitable doping levels and cap/buffer thicknesses, the resulting fermi level equalization (as in normal homo or heterojunctions) thereby allowed the setting or “pinning” of the superlattice Fermi level to any desired value within the range made available by the original bulk material characteristics in conjunction with the doping conditions. When the thicknesses of the InAs sandwiching layers became less than 1 μm, the sandwiching effect and the intersubband transition decreased dramatically. The structure of the interfaces inside the superlattice was also studied. Energy dispersive spectroscopy was used to estimate interdiffusion conditions within the superlattice. The effects of different periods and purge gases on the absorption spectra were also studied.
Physica E: Low-dimensional Systems and Nanostructures, 2005
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 ¼ 5 to 15. Photoluminescence and photoresponse measurements, performed at 80 K, displayed peak positions and cut-off wavelengths between 3.8 and 8.3 mm. 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 mm, an absorption coefficient value varying from 4 Â 10 3 to 5.5 Â 10 3 cm À1 in the 3-5 mm wavelength range, and a photovoltaic response up to 260 K. r
Physical Review B, 2002
Abrupt InAs/GaSb superlattices have In-Sb and Ga-As interfacial chemical bonds that are not present in the constituent materials InAs and GaSb. We study the effect of interfacial atomic mixing on the electronic structure of such superlattices, including electron and hole energies and wave function localization, interband transition energies, and dipole matrix elements. We combine an empirical pseudopotential method for describing the electronic structure with two different structural models of interfacial disorder. First, we use the ''single-layer disorder'' model and change in a continous way the composition of the interfacial bonds. Second, we study interfacial atomic segregation using a layer-by-layer kinetic model of molecular beam epitaxy growth, fit to the observed scanning tunneling microscopy segregation profiles. The growth model provides a detailed structural model of segregated InAs/GaSb superlattices with atomic resolution. The application of the empirical pseudopotential method to such structures reveals remarkable electronic consequences of segregation, among them a large blueshift of the band gap. This result explains the surprising gap increase with growth temperature observed for similar structures. In particular we find that ͑i͒ superlattices with only In-Sb interfacial bonds have lower band gaps ͑by 50 meV͒ than superlattices with only Ga-As interfacial bonds. ͑ii͒ Heavy-hole-to-electron transition energies increase with the number of Ga-As interfacial bonds more than light-hole-to-electron transition energies. ͑iii͒ The heavy-hole hh1 wave functions show a strong localization on the In-Sb interfacial bonds. The heavy-hole wave functions have very different amplitudes on the Ga-As interface and on the In-Sb interface. ͑iv͒ Sb segregates at InAs-on-GaSb growth, whereas As and In segregate at GaSb-on-InAs growth, but Ga does not segregate. ͑v͒ The segregation of Sb and In induces a blueshift in the band gap. ͑vi͒ There is an in-plane polarization anisotropy due to the low symmetry of the no-common-atom InAs/GaSb superlattice. This anisotropy is reduced by interfacial segregation.
Interface analysis of InAs/GaSb superlattice grown by MBE
(2007) Journal of Crystal Growth, 301-302 (SPEC. ISS.), pp. 889-892.
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.
2021
We have investigated in the bands structure and the effective mass, respectively, along the growth axis and in the plane of InAs (d1 =48.5A)/GaSb(d2 =21.5A) type II superlattice (SL), performed in the envelop function formalism. We studied the semiconductor to semimetal transition and the evolutions of the optical band gap, Eg (Γ), as a function of d1 , the valence band offset Λ and the temperature. In the range of 4.2–300 K, the corresponding cutoff wavelength ranging from 7.9 to 12.6 µm, which demonstrates that this sample can be used as a long wavelength infrared detector. The position of the Fermi level, EF = 512 meV, and the computed density of state indicates that this sample is a quasi-two-dimensional system and exhibits n type conductivity. Further, we calculated the transport scattering time and the velocity of electrons on the Fermi surface. These results were compared and discussed with the available data in the literature.
Journal of Applied Physics, 1995
Temperature dependent carrier dynamics in telecommunication band InAs quantum dots and dashes grown on InP substrates J. Appl. Phys. 113, 033506 (2013) Effects of pumping on propagation velocities of confined exciton polaritons in GaAs/AlxGa1−xAs double heterostructure thin films under resonant and non-resonant probe conditions J. Appl. Phys. 113, 013514 (2013) Sub-250nm light emission and optical gain in AlGaN materials J. Appl. Phys. 113, 013106 Infrared to vacuum-ultraviolet ellipsometry and optical Hall-effect study of free-charge carrier parameters in Mgdoped InN A series of five short-period (InAs)&4lSb), superlattices, grown either with ALAS-like, InSb-like, or alternating interfaces, were studied by means of x-ray diffraction, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, photoluminescence and ellipsometry. The combination of these techniques allows us to explain the pronounced differences in the optical and structural properties of both types of interfaces. In samples with an A&-like bottom interface x-ray, HRTEM and Raman results demonstrate the differing structural quality to be related to inhomogeneous strain relaxation and As intermixing. The energies of the critical points Ee , Et and Er +A\, of the samples with pure Ah&like interfaces are shifted by more than 100 meV to higher energies with respect to those of the samples with InSb-like interfaces. These differences can be understood on the basis of the different interfacial atomic structure and strain in the samples. 0 1995 American Institute of Physics.