Cryogenic Small-Signal Model for 0.55-μm Gate-Length Ion-Implanted GaAs MESFET’s

The cryogenic microwave performance of 0.5 ×300- m gate ion-implanted GaAs MESFET’s are presented. The devices studied here have been fabricated as part of a process control monitor chip (PCM) which uses comparable industry standard design rules. We have performed detailed small-signal element modeling to determine the temperature dependence of important physical parameters over a lattice temperature range from 300 K to 115 K. We find appreciable improvement in cut-off frequency and well behaved temperature dependence of transconductance (g_m) and gate-source capacitance (C_gs). Empirical relations for the temperature dependence of f_T, f_max,g_m, and C_gsthat should provide accurate temperature dependant device and circuit models, are presented.