Transparent ZnO ohmic contact on semi-insulating GaAs

We present a study of the ZnO/GaAs SI junction and its possible application in radiation detectors. Ion beam sputtered ZnO films obtained in a H-2 environment show low resistivity and very good optical transmission in the visible range. Current-voltage measurements reveal an ohmic behaviour of the ZnO contact on semi-insulating GaAs. To carry out an evaluation of the injection properties of the ZnO contact a ZnO/GaAs/Schottky structure has been realised. Under high reverse electric field (approximate to 4 x 10(4) V/cm) low minority injection from the ZnO contact has been observed. The same structure used as light detector has shown an efficiency of 34% for a bias of 600 V at a wavelength of 670 nm.