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

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