[001]-ORIENTED AND PIEZOELECTRIC-[111]-ORIENTED INAS GASB STRUCTURES UNDER HYDROSTATIC-PRESSURE/

Magnetotransport measurements have been carried out under hydrostatic pressure on [001]- and [111]-oriented InAs/GaSb structures grown by me tal-organic vapor-phase epitaxy. The system is semimetallic at zero pr essure, but as the pressure is increased, electrons, located in the In As layers, transfer back into the valence band of GaSb and a semimetal -to-semiconductor transition is observed. In double heterojunctions th e zero band overlap condition occurs at 14 and 17 kbar for the [001] a nd [111]A orientations, respectively. The band crossing at the interfa ce has been calculated self-consistently for the two orientations, tak ing into account the intrinsic and extrinsic origins of the carriers. This band overlap is found not only to be strongly orientation depende nt, approximately 60 meV larger in [111]A compared with [001], but als o to decrease at rates of 10 and 12 meV/kbar for the [001] and [111]A orientations, respectively. These rates are much larger than those det ermined from molecular beam epitaxy samples, but closer to the variati on with pressure of the band gaps of the bulk materials.