Change of gm(f) in LT-GaAs and LT-Al0.3Ga0.7As MISFETs with thermal stress

GaAs and Al0.3Ga0.7As layers grown by MBE at low temperatures (LT) and subsequently annealed at normal growth temperature (600°C) were used as insulators in the gate structure of GaAs MISFETs. We observed improvement in the transconductance (gm) frequency dispersion characteristics of MISFET devices when compared to that of MESFETs. The high resistivity of in-situ annealed LT-grown insulator layers are due to arsenic precipitates and deep centres. Under long-term operation these defects might migrate towards the interface and deteriorate the gn, frequency dispersion characteristics. To validate these MISFET devices for long-term operation, gm frequency dispersion studies were carried out before and after thermal stressing.