Impact Ionization In Gaas-mesfets - Comments

In the above-named work (see ibid., vol.11, p.113-15, March 1990), Hui et al. proposed a method to measure impact ionization current in GaAs MESFETs and evaluated the impact ionization coefficient alpha /sub n/ in GaAs. For electric fields greater than approximately 1.5*10/sup 5/ V-cm/sup -1/, alpha /sub n/ can be fitted to the equation alpha /sub n/=4.0*10/sup 6/*exp (-2.3*10/sup 6//E). In the present work, the commenters performed careful measurements of gate current I/sub g/ in GaAs MESFET devices similar to those used by Hui et al., and they show that the ionization coefficient still fits the above equation down to alpha /sub n/=10/sup -4/ cm/sup -1/. These results extend the previous data by three orders of magnitude. In a reply, the original authors affirm that the commenters have significantly improved the accuracy of the data previously presented.