Ultraviolet photoresponse properties of ZnO:N/p-Si and ZnO/p-Si heterojunctions

• The ZnO/p-Si and ZnO:N/p-Si heterojunctions have been successfully fabricated using spray pyrolysis deposition method.
• Both of undoped and nitrogen doped ZnO films are polycrystalline with (0 0 2) plane as preferential orientation.
• ZnO:N/p-Si heterojunction exhibits responsivity of 0.125 A/W at 5 V.
• The photocurrent reaches to its maximum value after 3 s and 1 s for ZnO/p-Si and ZnO:N/p-Si heterojunctions, respectively.

The ZnO/p-Si and ZnO:N/p-Si heterojunctions have been successfully fabricated using spray pyrolysis deposition method. ZnO:N is p-type with low resistivity of 0.254 Ω cm and high hole concentration of about 2.32 × 1019 cm−3. Both of undoped and nitrogen doped ZnO films are polycrystalline with (0 0 2) plane as preferential orientation. Photoluminescence spectrum is composed of an ultraviolet (UV) emission peak (about 3.26 eV) and two visible emission peaks in blue and green region. The dark and illumination current–voltage (I–V) characteristics show the typical rectifying behavior for the heterojunctions. The rectification ratio under UV illumination and responsivity of ZnO/p-Si are 194.13 (at 5 V) and 0.055 A/W (at −5 V), respectively. ZnO:N/p-Si heterojunction exhibits responsivity of 0.125 A/W at 5 V. The photocurrent reaches to its maximum value after about 3 s and 1 s for ZnO/p-Si and ZnO:N/p-Si heterojunctions, respectively. After 1 s, photocurrent decay 50% and 90% of initial value for ZnO/p-Si and ZnO:N/p-Si heterojunctions, respectively.