GROWTH OF INAS-ALSB QUANTUM-WELLS HAVING BOTH HIGH MOBILITIES AND HIGH-CONCENTRATIONS

Low-temperature mobilities in InAs-AlSb quantum wells depend sensitively on the buffer layer structures. Reflection high energy electron diffraction and x-ray diffraction show that the highest crystalline quality and best InAs transport properties are obtained by a buffer layer sequence GaAs --> AlAs --> AlSb --> GaSb, with a final GaSb layer thickness of at least 1 mum. Using the improved buffer scheme, mobilities exceeding 600,000 cm2/Vs at 10 K are routinely obtained. Modulation delta-doping with tellurium has yielded electron sheet concentrations up to 8 x 10(12) cm-2 while maintaining mobilities approaching 100,000 cm2/Vs at low temperatures.