Photocurrent Property of GaN on the Si Photodetector with a Nearly Polycrystalline α-Al₂O₃ Buffer Layer

Using nearly polycrystalline α-Al₂O₃ as the buffer layer, GaN epilayers were grown on Si (111) substrates by low pressure metalorgnic chemical-vapor deposition. The nearly polycrystalline α-Al₂O₃ was formed by anodic porous alumina annealed at high temperature. Prototype photoconductive detectors were fabricated with these materials. The spectral response of these detectors exhibits a relatively sharp cutoff near the wavelength of 360 nm and a peak at 340 nm with a shoulder near 360 nm. Under 5 V bias, the responsivities at 340 nm and 360 nm were measured to be 3.3 A/W and 2.4 A/W, respectively. The relationship between the responsivity and the bias voltage shows that the responsivity is saturated when the bias voltage reaches 5 V.