Monte Carlo simulation of InP and GaAs MESFETs

We have performed Monte Carlo simulations of InP MESFETs of lengths 0.6, 0.9 and 1.2 mu m and compared these results with those on GaAs MESFETs of the same dimensions. The direct current IV characteristics of the two materials were found to be similar though the GaAs characteristics were on the whole superior, reaching their operating point at lower drain voltages and possessing higher gains. However, oscillations in the drain current caused by changes in drain voltage in the GaAs devices were not present to the same degree in the InP devices. This difference is caused partially by the onset of the negative differential regime in InP at a higher electric field than in GaAs but the primary cause is the longer ballistic transport times in InP. This suggests that InP MESFETs may prove to have superior frequency response characteristics than GaAs MESFETs.