MOLECULAR-BEAM EPITAXIAL-GROWTH OF INAS/GASB DOUBLE QUANTUM-WELLS FOR COMPLEMENTARY HETEROJUNCTION FIELD-EFFECT TRANSISTORS

We report the molecular beam epitaxial growth of InAs/GaSb double quantum wells applied to complementary heterojunction field-effect transistors. The effect of silicon doping in various positions in the (AlxGa1-x)Sb barrier layers on the electrical characteristics of InAs and GaSb quantum wells was investigated. Compensation doping of silicon in the (AlGa)Sb barrier was always found to degrade carrier mobilities of both channels, suggesting substantial diffusion of acceptors in the barrier. A minimum of 150 angstrom was found to be necessary for the mid-barrier thickness between the channels in order to avoid the carrier transfer. Formation of an InSb-like bond at the InAs/(AlGa)Sb heterointerface by the proper sequential control of molecular beams was suggested by Raman scattering analysis. The proper shutter sequence was confirmed to be useful also in the InAs/GaSb double quantum well structure in order to obtain a high quality InAs channel. Vertically integrated enhancement mode GaSb p-channel heterojunction field-effect transistors (HFETs) and depletion mode InAs n-channel HFETs have been successfully fabricated. It became clear that the increase of compensation doping is not enough to turn the n-HFET into enhancement mode but cause parallel conduction in the barrier. Reduction of native donors will become essential for our goal.