The effects of electron beam irradiation damage has been investigated
in Si/SiGe heterostructures. The damage to SiGe two-dimensional hole g
ases (2DHGs) was measured as a function of accelerating voltage and el
ectron dose. For 40 keV electrons at a dose of 2 C m(-2) (typical PMMA
resist values), the material properties were not significantly altere
d. For 100 keV and higher energy electrons, the irradiated material be
came 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 d
evices were fabricated on high mobility SiGe two-dimensional electron
gases (2DEGs) using the damage technique and gated using Schottky gate
s. Plateaux were observed in the conductance as a function of gate vol
tage. Random telegraph signals (RTSs) were observed from a 10 mu m-wid
e Hall bar irradiated with 300 keV electrons at a dose of 10(5) C m(-2
). (C) 1997 Academic Press Limited