We show that ion-damaged GaAs may be used to detect millimeter electromagne
tic waves in photoconductive sampling gates. The semi-insulating GaAs mater
ial which was implanted with a dose of 10(14) cm(-2) protons at an energy o
f 200 keV gave a signal to noise improvement of about 11.4 dB when compared
with as-grown semi-insulating GaAs. The improvement is in spite of a reduc
ed carrier mobility in the ion-implanted material and is due to the shorter
carrier lifetime and formation of ohmic contacts with the ion-damaged semi
-insulating GaAs. (C) 1999 American Institute of Physics. [S0003-6951(99)01
532-6].