Growth of Thick Ge Epilayers on Si(100) Substrates Utilizing Two-Step Approach by Ultrahigh Vacuum Chemical Vapor Deposition

Abstract

Ge epilayers on low temperature (LT) Ge buffer layers were grown by ultrahigh vacuum chemical vapor deposition using the two-step approach. Effects of the growth temperature and the thickness of the low temperature Ge buffers were studied. It was demonstrated that it was unable to obtain flat LT Ge buffers just through lowering the growth temperature due to the ultraslow grow rate that 3D islands formation couldnt be prohibited. However, the rough LT Ge surface was smoothed by subsequent growth at elevated temperature if the LT Ge layer was thick enough and the compressive strain was relaxed largely, and the detrimental Si-Ge intermixing was effectively prohibited as well. When using proper growth conditions for the low temperature Ge buffer, thick Ge epilayer with a low threading dislocation density and a smooth surface was obtained.