Cyclotron resonance in InAs/GaSb heterostructures

Abstract

Cyclotron resonance measurements are reported for both electrons and holes in type II InAs/GaSb superlattices and double heterostructures (OHETS). Superlattice (multi quantum well) samples of InAs/GaSb grown by MOVPE have sufficiently high hole gas mobilities and densities to allow t h e first measurements of hole cyclotron resonance in this system. The measured hole masses are -0.lm. and 0.2 m. . indicating a large reduction over the bulk values d u e lo the decoupling of the valence band by strain and confinement. This is ingood agreement with eight-band k . p theory reported here, and previous calculations. The electron masses in both superlattices and OHETS are found to be strongly influenced by non-parabolicity and the carrier concentration. leading lo considerable increases over the band edge values. Similar values are found for both electron and hole masses in structures grown along both [OOI] and [111JA directions

Probing the semiconductor to semimetal transition in InAs/GaSb double quantum wells by magneto-infrared spectroscopy

“…We find that close to the dilute limit, the band inversion significantly modifies the magneto-absorption of the system, giving rise to multiple absorption peaks with distinct non-linear Bdependence. All the major absorption peaks observed in our experiment can successfully be explained using an eight-band PB model, with semi-quantitative agreement surpassing the previous two-band and eight-band models 3,6 . We thank Danhong Huang for helpful discussion.…”

“…Based on our self-consistent eight-band k · p calculation (to be elaborated later), the d = 8 nm sample is in the normal state, the d = 10 nm sample is close to the critical state and the d = 11, 13, and 15 nm samples are in the inverted state. Magneto-transport measurements determined the carrier densities to be as low as n ∼ 1 × 10 11 cm −212 , several times lower than that reported in previous studies [1][2][3]5,6 . Therefore, our samples are close to the dilute limit, particularly suited for magneto-optical spectroscopy studies.…”

“…Our work paves the way for band engineering of optimal InAs/GaSb structures for realizing novel topological states as well as for device applications in the terahertz regime. Broken-gap InAs/GaSb double quantum wells (DQWs) have long been important in studying intriguing phenomena, ranging from excitonic resonances 1,2 , electron-hole hybridization [3][4][5][6] , the quantum spin Hall (QSH) effect [7][8][9] , helical Luttinger liquids 10 , to the exciton insulator 11 . The novel properties of the InAs/GaSb system stem from its peculiar band-edge alignment, in which the bottom of the InAs conduction band lies below the top of the GaSb valence band ( Fig.…”

“…Practical applications of the material require a complete understanding of the electronic band structure, with respect to external parameters such as strain and doping. Previous combined experimental and theoretical studies [3][4][5][6] largely focused on the heavily inverted regime using reduced models. Quantitative investigations of the transition from the normal to the inverted state have not yet been performed.…”

Magneto-infrared modes in InAs-AlSb-GaSb coupled quantum wells

“…On one hand, the results suggest the formation of stable excitons by showing exciton's 1s − 2p internal transitions; 66-68 on the other hand, they were interpreted as the hybridization gap due to a mixing of the electron and hole wavefunctions. [77][78][79][80][81][82][83][84][85][86][87][88] Though most of the FIR investigation reveal multiple modes around CR in InAs/GaSb CQWs, only a single mode was observed up to 12 T and interpreted as electron-CR by Heitmann et al 89 Earlier studies in InAs/GaSb superlattice systems show electron CR, intersubband transitions and sometimes two absorptions near CR attributed to two occupied electron subbands. [90][91][92][93][94] More recent reports about the InAs/GaSb 2DEHS demonstrate results in favor of the hybridization gap interpretation.…”