Molecular beam epitaxy of gallium arsenide using direct radiative substrate heating

Abstract

Conventional mounting techniques in molecular beam epitaxy using indium to solder GaAs substrates to molybdenum blocks result in a rough back side which is incompatible with integrated circuit processing. We present the design of a new substrate holder which allows direct radiative heating of substrates without use of indium bonding. Temperature measurement and control are done by radiative coupling to a shielded thermocouple which sits just behind the GaAs wafer. Excellent temperature uniformity is achieved over a 3 in. wafer by a molybdenum holder ring design which minimizes contact with the substrate and holds the wafer against the back of the ring to eliminate shadowing of the substrate from the heater. No coating of the wafers is necessary for temperature control. Stress related defects and growth induced wafer warpage are not observed. Deep level transient spectroscopy, photoluminescence, and mobility measurements show the clear superiority of GaAs layers grown using direct radiative substrate heating compared to conventional indium bonding.