ABSTRACT

Remote doping of InAs/GaSb quantum wells presents a problem with molecular beam epitaxy (MBE). Silicon, which is the preferred MBE dopant for other III-Vs, acts as an acceptor with GaSb. Use of a group VI dopant risks long term memory effects. An alternative technology has been developed employing a double well structure where the second InAs well is thin ( ~ 2nm) and highly doped with silicon. Because of the high confinement energy this well acts as a source of electrons for the first well. Conductivities as high as 10-1S at 4K can be achieved with a mobility of 185,000 cm2/Vs. Higher electron concentrations are possible but the mobility falls, probably due to intersubband scattering when the second subband becomes occupied. A self-consistent modelling programme has been developed to describe the electron transfer. The model includes i) the nonparabolicity of the InAs conduction band, ii) the 2D hole gas in the GaSb and iii) the surface pinning of the Fermi energy due to the presence of surface donors in the GaSb.