Growth of Ge epilayers using iso-butylgermane (IBGe) and its memory effect in an III-V chemical beam epitaxy reactor

Abstract

Employing group IV semiconductors as germanium (Ge) and III-V compounds as heterostructures it enables efficient devices such as triple junction solar cells, thermophotovoltaic and infrared detection devices. In this work, we studied the growth of Ge with iso-butylgermane (IBGe) as germanium source and the Ge memory effect in our VG Semicon V90F 4-inch chemical beam epitaxy (CBE) reactor for III-V materials. High crystalline quality Ge epilayers were grown on GaAs substrates, while a Ge background doping in the range of 5 × 1018 cm−3 has been found in the GaAs epilayers. The low temperature photoluminescence (LTPL) spectra showed that the Ge background leads to a blueshift and broadening of the exitonic transition in the grown GaAs layers. To eliminate the Ge memory effect several approaches of chamber bake have been investigated, and a reduction of more than one order of magnitude have been demonstrated. Hall effect and secondary ion mass spectroscopy (SIMS) measurements corroborate the reduction in Ge background doping in GaAs epilayers down to 1 × 1017 cm−3.