Intrinsic response time measurements in uniform and nonuniform field avalanche regions in GaAs

Experimental determination of the intrinsic avalanche response time τ1in GaAs microwave diodes shows good agreement with theoretical predictions for structures having uniform electric fields in the avalanche region as opposed to those with nonuniform profiles. Measurements are presented for a high-power GaAs double-drift Read diode, a single drift X-band Read diode and a 35-GHz Lo-Hi-Lo bathtub structure to demonstrate the agreement. The agreement of these results with calculations that neglect high field diffusion indicates that high field diffusivity is not very important in GaAs avalanche regions as narrow as 2000 Å. The value of τ1, for the high-power double-drift diode obtained from high-frequency noise measurements, was found to be in agreement with the value obtained for the same diode by Adlerstein et al., where τ1was obtained from microwave admittance data. Experiments indicate that observed variations in the value of τ1due to changes in the junction temperature are consistent with variations due to the temperature dependence of the scattering limited velocities. It is further concluded that consistent discrepancies found between theory and experiment for structures having nonuniform fields in the avalanche region are the result of nonlocal effects in GaAs.