Fabrication Of Sige Quantum Devices By Electron-Beam Induced Damage

The effects of electron beam irradiation damage has been investigated in Si/SiGe heterostructures. The damage to SiGe two-dimensional hole gases (2DHGs) was measured as a function of accelerating voltage and electron dose. For 40 keV electrons at a dose of 2 C m(-2) (typical PMMA resist values), the material properties were not significantly altered. For 100 keV and higher energy electrons, the irradiated material became more resistive at 300 K as the electron energies were increased. The material became highly resistive at low temperatures and froze out at between 20 and 30 K. The 2DHGs also became more resistive at 300 K when the irradiation dose was increased. A number of narrow channel devices were fabricated on high mobility SiGe two-dimensional electron gases (2DEGs) using the damage technique and gated using Schottky gates. Plateaux were observed in the conductance as a function of gate voltage. Random telegraph signals (RTSs) were observed from a 10 mu m-wide Hall bar irradiated with 300 keV electrons at a dose of 10(5) C m(-2). (C) 1997 Academic Press Limited