A REVIEW ON ZnO HETEROJUNCTION PHOTODETECTOR FOR UV APPLICATION

Hetero-structured photodetector is a rapidly growing field of optoelectronic sensing for designing ultraviolet photodetectors of high efficiency and high responsivity. In recent years, one of the next generation semiconductor material ZnO, has attracted much attention in shorter wavelength optoelectronics devices and sensors. ZnO is considered as an ideal candidate in UV region because of its large exciton binding energy (60 meV), and wide bandgap energy (3.37eV). Naturally ZnO has n type conductivity and is very difficult to produce p type ZnO. Various p type materials such as Si, GaN, NiO, and Sr2Cu2O2 have been used to realize p-n hetero junction photodetector. ZnO/Si based heterojunction devices have good electrical and optical properties, are easy to fabricate and has low deposition temperature. GaN is one of the propitious material in terms of considerably small lattice mismatch, less than 1.8% with ZnO and also exhibits similar lattice structure (wurtzite). ZnO/GaN structure exhibits high UV to visible rejection ratio and is very useful for high sensitive UV applications. The responsivity of n type ZnO with Si and GaN as substrate material is analyzed in this work. Also analyzed the various parameters that affects the responsivity of photo detector.