A comparative study of reliability of GaAs MESFETs with TiAl and TiPtAu gate at elevated temperature and high current density

A comparative study of the performance degradation of GaAs MESFETs with TiAl and TiPtAu gates at elevated temperature and high current density is presented. Results show that (1) the increase in gate series resistance R/sub g/ is a main factor that leads to increase in ideality factor n of TiAl and TiPtAu gate Schottky diodes. (2) The TiAl gate Schottky diode performance (gate series resistance R/sub g/, ideality factor n, barrier height /spl Phi//sub b/) degrades rapidly whereas the device parameters such as maximum drain saturation current I/sub dss/, open channel resistance R/sub 0/ below the gate, pinch-off voltage V/sub p0/ etc., remain fairly unchanged. (3) For the TiPtAu gate MESFET, with suitable annealing, the Schottky diode performance (ideality factor n, barrier height /spl Phi//sub b/) remains stable whereas the device parameters such as maximum drain saturation current I/sub dss/, open channel resistance below the gate R/sub 0/, pinch-off voltage V/sub p0/, the transconductance g/sub m/ etc. degrade rapidly. The performance degradation of the two types of MESFET forms a sharp contrast.