High-field phenomena and reliability issues in microwave heterojunction FETs

This work overviews different issues connected with high electric field conditions in power microwave AlGaAs-GaAs heterojunction FETs (HFETs). These conditions and possible attendant degradation mechanisms, are likely to take place when devices are operated at high drain voltage for power amplification. Typical degradation modes described in this paper include drain current and transconductance reduction (and power slump). A physical interpretation of the experimental results is given with the support of numerical device simulations. The non-trivial relationship between the drain-gate HFET breakdown voltage and the device reliability is also discussed in some detail.