Enhanced UV Photodetector Efficiency with a ZnO/Ga<sub>2</sub>O<sub>3</sub> Heterojunction
Shashi Pandey, Swaroop Ganguly, Alok Shukla, Anurag Tripathi
Abstract
Heterostructures comprising uncoated ZnO and coated with thin layers of Ga 2 O 3 were produced by using spin-coating and subsequent hydrothermal processing. X-ray diffraction examination verifies the structural integrity of the synthesized heterostructures (HTs). Optical and photoluminescence spectra were recorded to assess the variation in absorption and emission of the Ga 2 O 3 -coated HTs in comparison to those of the pristine ZnO. We conducted comparative density-functional theory (DFT) computations to corroborate the measured bandgaps of both categories of HTs. To assess the stability of our devices, the transient response to on/off light switching under zero bias has been studied. A rise time τ r1 (τ r2 ) of 2300 (500) ms and a decay time τ d1 (τ d2 ) of 2700 (5000) ms have been observed for bare ZnO and ZnO/Ga 2 O 3 HTs, respectively. A significant change was also observed in the electrical transport properties from bare ZnO to ZnO/Ga 2 O 3 . To see the performance of the device, responsivity ( R ) and detectivity ( D = 1/NEP B ) have been measured. It is evident from observation that responsivity of a device shows a maximum value in the UV region, while it is reduced in the visible region for HTs. In the case of detectivity, the maximum value reached was 145 × 10 14 Hz 1/2 /W (at ∼200 nm) and 38 × 10 14 Hz 1/2 /W (at 300 nm) for Ga 2 O 3 -coated ZnO and bare ZnO HTs, respectively. The maximum responsivity measured for the bare ZnO HTs is 7 (A/W), while that of Ga 2 O 3 -coated ZnO HTs is 38 (A/W). This suggests a simple way of designing materials for fabricating broad-range cost-effective photodetectors.