Oscillation and Photoresponse of High-Resistivity n-GaAs Diodes

Abstract

Diodes of lengths 0.17 mm and 1 mm with ohmic contacts were made from n-type, ~ 16 Ωm-resistivity GaAs. The diode resistance varies with temperature as exp (−Δ*/kT), with Δ** 412 meV. Above a threshold voltage of 50 to 80 V, depending on the diode, a small current oscillation occurs in the short diodes, which can be explained by the periodic propagation of small high-field domains at a velocity of the order of 1 m/s at room temperature. Several features of the transient response of the diodes to pulses are consistent with the occurrence of weak field-enhanced trapping effects which could account for the formation of the high-field domains.The long diodes exhibit a novel photoelectric effect: if a diode is illuminated and is subjected to a high-voltage step, the current assumes initially a value proportional to the voltage. Then, in about 1 μs, it decays by as much as 92% of its initial value. All the characteristics of this effect can be explained in terms of accumulation of minority carriers (holes) at the cathode of the diode (which is blocking for holes).