Low-dimensional inverted Si/SiGe modulation-doped electron gases using selective ex-situ ion implantation

A novel fabrication technique for selectively modulation-doping strained-Si quantum wells on relaxed Si1−xGex substrates to produce field effect transistors and low dimensional devices is demonstrated using standard silicon processing techniques. Strain–relaxed Si1−xGex buffers were selectively ion implanted ex-situ through a lithographically patterned resist before being chemically cleaned and replaced in the growth chamber to regrow a quantum well and cap layers. Mobilities of up to 49,900 cm2 V−1 s−1 for a carrier density of 9.72×1011 cm−2 at 1.7 K for selectively doped Hall bars have been demonstrated along with wires using the technique.