p - Zn O ∕ n - Si heterojunction: Sol-gel fabrication, photoresponse properties, and transport mechanism

p - Zn O ∕ n - Si heterojunction is achieved by depositing Al–N codoped p-type ZnO film on n-Si by low-cost sol-gel technique. The junction shows good diode characteristics with rectification ratio (IF∕IR)∼10 at 4V in the dark. The photoresponse of the heterojunction is investigated by studying the current-voltage characteristics under the ultraviolet (370nm) and visible light (450nm) illuminations. By fitting the experimental data, we have proposed the current transport mechanism to be dominated by the recombination tunneling at lower and by the space-charge limited current at higher forward voltages, which are further supported by the photocapacitance and photocurrent spectra.