Direct observation of dislocation effects on threshold voltage of a GaAs field-effect transistor

The threshold voltage of a GaAs metal-semiconductor field-effect transistor (MESFET) fabricated on a liquid encapsulated Czochralski grown, semi-insulating substrate was found to be influenced by growth-induced dislocations. Field-effect transistors located at less than 20–30 μm from a dislocation exhibited a threshold voltage lower than that of FET’s located far from a dislocation. The maximum difference in threshold voltage of FET’s located at less than and more than this critical distance was obtained to be about 300 mV. The first definitive correlation between dislocations and FET threshold voltage is reported.