Structural, Electrical, and UV Detection Properties of ZnO/Si Heterojunction Diodes

This paper reports the structural, electrical, and ultraviolet (UV) light detection properties of n-ZnO/p-Si heterojunction diodes. The ZnO nanocrystalline thin films were deposited over p-Si (100) substrates using RF sputter deposition. The structural and surface morphological properties of the deposited films were studied using X-ray diffractometry, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Results confirm the preferred c-axis growth of the nanocrystalline films with hexagonal wurtzite structure. The junction properties of ZnO/Si heterojunction diodes were investigated using current-voltage and capacitance-voltage measurements. The fabricated diodes exhibit a high rectification ratio of similar to 840 at +/- 5 V. The ideality factor of the fabricated diodes was found to decrease from 3.2 to 1.7 when measurement temperature was increased from 303 to 403 K, whereas the barrier height increased from 0.74 to 0.96 eV in the same temperature range. Various other parameters, such as built-in potential, donor concentration, and depletion width, have also been evaluated. The UV detection properties of our fabricated structures were investigated using a UV lamp of 365-nm wavelength. The fabricated diodes show a very good response toward UV light. The values of responsivity and detectivity were found to be 0.35 A/W and 4.16 x 10(9) mHz(1/2)W(-1), respectively.