Experimental Study of Deep Levels in MESFETs

We have induced the formation of deep levels in the active channel of GaAs MESFET's by exposing these devices to high fluence of energetic neutrons. A result, we have measured a modification of the main DC parameters, i.e. decrease of I DSS , gm and V p . By using an experimental technique based on the frequency dispersion of the device transconductance, gm(f), we have been able to indentify at least one of the type of the defects (U-band) introduced in the GaAs substrate by irradiation.