Abstract
The in-plane optical anisotropy (IPOA) in InAs/GaSb superlattices has been studied by reflectance difference spectroscopy (RDS) at different temperatures ranging from 80 to 300 K. We introduce alternate GaAs- and InSb-like interfaces (IFs), which cause the symmetry reduced from D2d to C2v. IPOA has been observed in the (001) plane along [110] and [11¯0] axes. RDS measurement results show strong anisotropy resonance near critical point (CP) energies of InAs and GaSb. The energy positions show red shift and RDS intensity decreases with the increasing temperature. For the superlattice sample with the thicker InSb-like IFs, energy positions show red shift, and the spectra exhibit stronger IPOA. The excitonic effect is clearly observed by RDS at low temperatures. It demonstrates that biaxial strain results in the shift of the CP energies and IPOA is enhanced by the further localization of the carriers in InSb-like IFs.
Highlights
InAs/GaSb type-II superlattices (SLs) are a considerable interest in the application of middle and far infrared photodetection
If SLs are pseudomorphic-grown on GaSb substrate, the strains of GaAs, InAs, and InSb are determined by the substrate, which can be calculated by: eiz
The average lattice constant of superlattice is increased as a result of red shift energies of the critical point (CP)
Summary
InAs/GaSb type-II superlattices (SLs) are a considerable interest in the application of middle and far infrared photodetection. These structures have broken-gap band alignment, which allows tuning optical and electronic properties by varying layer thickness [1,2]. As the InAs and GaSb share no common atoms (NCA) across the interface (IF), these IFs have to be controlled by both InAs-like, both GaSb-like or alternating InAs- and GaSblike. This kind of CA/C’A’ zinc blende heterostructures lost their ideal Td point-group symmetry along the [001] growth direction. If SLs have only one type of IF such as C-A’ or C’-A, it exists a S4 rotation-reflection axis, the symmetry is described as D2d point-group symmetry
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