INFLUENCE OF STRAIN ON ELECTRICAL-PROPERTIES OF THE GE CHANNEL IN THE MODULATION-DOPED P-SI0.5GE0.5/GE/SI1-XGEX HETEROSTRUCTURE

The influence of strain on the electrical properties of the Ge channel in a modulation-doped p-Si0.5Ge0.5/Ge/Si(1-x)Ge(x) heterostructure is studied in relation to the Si mole fraction (1-x) and the thickness of the Si(1-x)Ge(x) buffer layer. In the range of 1-x-less-than-or-equal-to 0.25, the hole concentration and mobility increase with strain in the Ge channel. However, in the range of 1-x > 0.25, they decrease with strain due to the large number of threading dislocations. It is also found that hole concentration and mobility increase with buffer layer thickness. As a result, a very high mobility of 7600 cm2.V-1.S-1 at 77 K is obtained at a Si mole fraction of 0.25 and buffer layer thickness of 1-mu-m.