Growth of ultrahigh mobility SiGe/Ge/SiGe heterostructures with very small parallel conduction and their device application

Strained Ge channel structures on SiGe virtual substrates are promising for ultrahigh speed p-type devices because of their extremely high hole mobility. We have recently reported that the drift mobility at room temperature (RT) of the 2-dimensional hole gas (2DHG) in strained Ge channels reaches to as high as 2940 cm/sup 2//Vs, which confirmed, for the first time, the expected mobility increase higher than the bulk Ge mobility, due to the strain. However, in samples reported so far, there exists a large amount of parallel conduction in thick SiGe buffer layers, which significantly decreased the overall mobility (RT Hall mobility was around 1300 cm/sup 2//Vs) and degraded the device performances. In this study, to overcome this problem, we employed Sb doping in Si/sub 0.3/Ge/sub 0.7/ buffer layers and successfully obtained almost parallel conduction free strained Ge channel structures.