Ultrafast response of multi-energy proton-bombarded GaAs photoconductors

Abstract

We have investigated the ultrafast optical and optoelectronic characteristics of multi-energy proton-bombarded GaAs (GaAs:H+) material and devices in some detail. Photo-excited carrier lifetimes of GaAs:H+ were observed to be as low as 350 +/- 50 fs. Photoconductive switches (PCS) fabricated on GaAs:H+ were found to exhibit lower dark currents (15 nA at a bias of 10 V) and higher breakdown voltage (> 100 kV/cm) than PCS's fabricated on semi-insulating (S.I.) GaAs. The temporal response of the GaAs:H+ PCS was about 2 ps at full-wave half minimum. Optically excited terahertz (THz) radiation from GaAs:H+ was reported for the first time to our knowledge. The temporal response and spectral bandwidth of the emitted THz radiation were 0.7 ps and 1.25 THz, respectively. The field strength of the THz signal was about 20 mV/cm. From the THz data, we are able to deduce that the effective carrier mobility of GaAs:H+ was less than 1 cm(2)/V-sec.