Effect of deep levels on the photo-sensitivity in GaAs substrate and MESFET device

Deep levels in SI-GaAs substrate, ion implantation layer and MESFET device have been investigated by photo-stimulated current measurement system (PSCS) using illumination in range of 700 nm to 3500 nm. It shows that there exists an absorption peak (1.42) and 1.20, 0.70, 0.48 eV deep levels in both SI-GaAs substrate, ion implantation layer and MESFET device. These deep levels have effect on the photosensitivity of the devices. These deep levels perhaps originate from SI-GaAs substrate which also has these levels. The way to decrease the photosensitivity in the device is discussed according to the result.