GaAs pulse-generating avalanche trap and recovery (avatar) diode

Abstract

A large-amplitude, subnanosecond-rise-time, pulse-generating GaAs diode has been developed. The diode has a v-n structure; the v-region was made by diffusing iron into n-GaAs. The iron in the diffused layer was detected by mass-spectrometer analysis; the depth of the diffused layer was of the order of 10 rm. Electrical contacts were formed by gold-germanium or indium alloying techniques. Compensation of carriers by diffusion of iron must be controlled precisely to produce pulse generation. The pulse generation could not be observed when the diffused layer converted to p-When the diode voltage and current exceeded a certain value, the diode switched between a low-current, high-voltage state and a highcurrent, low-voltage state. The high-current state due to the holes created by avalanche continued only for a short time interval. After an interval equal to the hole trapping time, the diode voltage again built up to the initial value. The pulse width varied from 1O"J to lo-? second d2pending on the length of the external transmission line. The minimum pulse width is limited by the rise time of the pulse. This may be improved by reducing the effective area and the series resistance of the diode. A typical pulse has an output voltage of 10 volts and a half-width of 500 picoseconds.The pulse repetition rate was varied from lo4 to lo5 Hz by means of a dc bias current.The experimental results with the diode may be summarized as foilows: (1) A very fast rise time of a few hundred picoseconds; (2) a large output voltage up t o 50 volts with a 5o-ohm load; (3) the pulse repetition rate varies with dc bias current. A pulse generator has been built as a test.type. 152