LAUSR

Al–ZnO/(n)Si and Al–ZnO/(p)Si heterojunction structures were fabricated by RF-sputtering of Al–ZnO thin film on Si substrates and their electrical and photoresponse properties were comparatively analyzed. The Al–ZnO/(n)Si heterojunction exhibited excellent diode behavior with an equivalent barrier height of 0.72 eV and an rectification ratio of $6.7 \times 10^{3}$ at ±0.5 V, while no rectifying behavior was observed for Al–ZnO/(p)Si device. Illuminated I–V analysis performed with different light intensities revealed excellent photoresponse properties and the strong dependence of the photocurrent on external bias for both Al–ZnO/(n)Si and Al–ZnO/(p)Si structures. The Al–ZnO/(n)Si structure requires smaller reverse bias than Al–ZnO/(p)Si for similar photoresponse. Based on dark I–V, illuminated I–V, and the energy band diagrams, photoresponse mechanisms were explained. In order to further understand the photoresponse mechanisms, quantum efficiency measurements were carried out, with applied external voltage bias. A general descriptive model was presented for the first time for the photogenerated current density in both Al–ZnO/(n)Si and Al–ZnO/(p)Si heterojunctions at different voltage bias.