Physical Limitation on Drain Voltage of Power PM HEMT

The electrical source-drain breakdown mechanism of pseudomorphic (PM) HEMTs has been studied in a pulse and DC regimes. It has been revealed that a maximum drain voltage is limited by an avalanche injection breakdown of the undoped i-GaAs layer (buffer). It has been established that observed breakdown is the result of the mutual intensification of an avalanche generation rate near the drain and an injection level from the source contact. Depending upon a gate bias the evolution of the observed breakdown results in a sharp drain current increase with a positive or negative differential conductivity (NDC). The NDC results in the HEMT switching to a state with current filaments and may result in the following local burnout. This following electrical burnout is defined by thermal heating and sinking conditions of the HEMT active area in the current filament state.