Influence of domain formation on the V/sub ds/ dependence of noise and gate leakage in InGaAs FETs

摘要

A model for high gate leakage currents in InGaAs-channel FETs is described. Such leakage is caused by running gate metal down an unpassivated mesa. Even when an airbridge is used, gate leakage is higher than anticipated from the sum of source-gate and drain-gate diode currents. Measurements of typical leakage and transconductance for a 1 mu m HFET at V/sub ds/=2 V are presented. The leakage is much higher than that observed at V/sub ds/=0 V. It is shown that, in JFETs and HFETs, reducing the doping level leads to a near-exponential decrease in leakage currents. Properly designed HEMTs can have low gate leakage in the high gain region.