Excess Gate Current Due to Hot Electrons in GaAs Gate FETs

We report on the first observations of hot electron effects in the gate current of GaAs-gate FET’s. We have made and tested a variety of these FET’s using MBE-grown material with 60nm and 35nm thick Al.4Ga.6As gate insulator layers. In measurements at 300K and 77K these devices show drain-voltage-dependent gate current substantially exceeding that which would be expected on the basis of simple vertical transport measurements. We attribute this current to the real-space transfer of hot electrons from the channel of the device into the (Al,Ga)As/GaAs barrier, from which they are collected into the gate.