Responsivity improvement of packaged ZnMgO solar blind ultraviolet photodetector by a sealing treatment of silica gel
Packaging is one of the most important procedures of the fabrication of photoelectric device such as ZnMgO solar blind ultraviolet (UV) photodetectors. The roles of packaging are: Electrically interconnecting unpackaged photodetector and pin as well as fixing it, and protecting unpackaged photodetector from external dirt, humidity and atmosphere. Nowadays, the researches of the ZnMgO solar blind UV photodetectors are well developed. However, the researches of packaging of these photodetectors are seldom. In this paper, we focus on the packaging of ZnMgO solar blind UV photodetectors. After a direct wire bonding method between steel wires and unpackaged photodetector by conductive silver adhesives and a sealing treatment by silica gel, the ZnMgO photodetector is packaged, and the responsivity of the device increases after the packaging. A -3 dB cutoff wavelength of 295 nm and a responsivity of 191 A/W are achieved under a bias of 10 V. The 90-10% decay time of the device is 280 ms, and the dark current of the device is 115 pA under a bias of 10 V. Moreover, the stability of the ZnMgO-based solar blind photodetector is obviously improved according to the well sealed packaged structure.