High-performance broadband photodetectors based on sputtered NiOx/n-Si heterojunction diodes

Abstract

High-performance broadband photodetectors based on NiOx/n-Si heterojunction were fabricated by radio frequency (rf) sputtering of NiO target at room temperature using 40, 60 and 80 W of power. The open circuit voltage is almost independent of the rf power with value of ∼0.33 V under illumination with red light with optical power of 3.71 mW/cm2, while the short circuit current depends on the sputtering power and has the highest value of 1.3 × 10−7 A (J = 1.45 × 10−3A/cm2) for diodes fabricated at 60 W. The responsivity (R) and specific detectivity in self-powered mode (Vb = 0 V) are higher for the 60 W photodiodes. The R values are 0.39, 0.61, 0.67 and 0.95 A/W under illumination with red, green, blue and UV lights with optical powers of 3.71, 1.03, 1.31 and 0.335 mW/cm2. The On/Off ratio of these diodes at Vb = 0 V is 1.5 × 104, 6.7 × 103, 9.4 × 103, 9.4 × 103 for illumination with the four lights. Capacitance-Voltage measurements indicate high quality of the NiOx/Si interface with low interface defect density and low density of bulk traps in NiOx for diodes obtained at the three powers. The responsivity of the heterojunction diodes obtained at 60 W at Vb = 0 V is among the highest reported in the literature for photodiodes based on NiOx. The quality of the rf sputtered NiOx layers and the low deposition temperature make them attractive for application in flexible optoelectronic devices.