MAGNETOTRANSPORT MEASUREMENTS ON INAS-GASB QUANTUM-WELLS WITH THE APPLICATION OF HYDROSTATIC-PRESSURE

We present a series of magnetotransport measurements on high mobility single InAs-GaSb semimetallic quantum wells using hydrostatic pressure s up to 10 kbar and temperatures down to similar to 100 mK. Clearly de fined, hole-related peaks in rho(xx) close to integer electronic filli ng factors in the semimetallic regime, have a stronger temperature dep endence than the electron Shubnikov-de Haas effect at millikelvin temp eratures and with this additional structure, apparent in rho(xx) the q uantum Hall plateaux in rho(xy) deviate from h/ve(2), where v is the f illing factor. The decrease in the electron concentration, dn(0)/dp is 3.0 x 10(10) cm(-2) kbar(-1) in the dark, and 4.0 x 10(10) cm(-2) kba r(-1) in the dark following infrared illumination to reduce the Fermi energy. We relate this reduction in the electron and hole concentratio ns to the uncrossing of the InAs conduction band and the GaSb valence band and to the role played by a GaSb surface donor at high pressures. The fermi energy at the surface is pinned approximately 250 meV above the GaSb Valence band edge.