High hole mobility in SiGe alloys for device applications

We report high hole mobility in modulation-doped SiGe alloys with Ge content up to 80%. The layers which are grown using ultrahigh-vacuum chemical vapor deposition are of high crystalline quality, have smooth surfaces, and have a low density of misfit dislocations. As a result of strain and high Ge content, we have measured hole mobilities in the range of 800–1050 cm2/V s at room temperature, and 3300–3500 cm2/V s at 77 K. The corresponding two-dimensional sheet hole density is about 3×1012 cm−2. Those numbers are, to our knowledge, the highest numbers ever reported for a SiGe alloy. The resistivity of this two-dimensional hole channel at room temperature is, to our knowledge, the lowest for any p-type semiconductor quantum well.