Effect of LT-layer thickness on the performance of LT-GaAs and LT-Al/sub 0.3/Ga/sub 0.7/As MISFETs

GaAs MISFETs with low temperature (LT) grown gate insulator layers have been fabricated and their electrical properties analyzed. The transconductance frequency dispersion characteristics of thinner (250 /spl Aring/ and 500 /spl Aring/ thick) LT-GaAs and LT-Al/sub 0.3/Ga/sub 0.7/As MISFETs are better than those of thicker (2000 /spl Aring/ and 1000 /spl Aring/ thick) LT-GaAs MISFETs. LT-Al/sub 0.3/Ga/sub 0.7/As and thinner LT-GaAs samples exhibited 1/f noise, while thicker LT-GaAs samples exhibited 1/f/sup 3/2/ noise with 500 Hz corner frequency. The noise parameter /spl alpha//sub latt/ was found to be of the order 1.0/sup -4/ for thinner LT-GaAs samples and for all of the LT-Al/sub 0.3/Ga/sub 0.7/As samples. From the DC characteristics, it was found that thinner LT-layer insulators are ideal for achieving higher transconductance without sacrificing the RF power handling capability. Our simulation results on 500 /spl Aring/ thick LT-Al/sub 0.3/Ga/sub 0.7/As MISFET devices showed power handling capability of 1.8 W/mm for a gate bias of -2 V and drain bias of 18.5 V at 1.1 GHz.