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_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_g, ideality factor n, barrier height Φ_b) degrades rapidly whereas the device parameters such as maximum drain saturation current I _dss, open channel resistance R₀ below the gate, pinch-off voltage V_p0 etc., remain fairly unchanged. (3) For the TiPtAu gate MESFET, with suitable annealing, the Schottky diode performance (ideality factor n, barrier height Φ_b) remains stable whereas the device parameters such as maximum drain saturation current I_dss, open channel resistance below the gate R₀, pinch-off voltage V_p0, the transconductance g_m etc. degrade rapidly. The performance degradation of the two types of MESFET forms a sharp contrast