In recent years, ZnMgO semiconductor alloys, with a direct bandgap tunable between 3.37 eV and 7.8 eV, become one of the most suitable materials for the fabrication of ultraviolet detectors. In this paper, we have fabricated metal-semiconductor-metal photodetectors on 1-μm thick Zn_0.8Mg_0.2O films. The interdigital metal electrodes are 500 μm long and 5 μm wide with an interelectrode spacing 2 μm, 5 μm and 10 μm, respectively. Zn_0.8Mg_0.2O films were grown on quartz by ratio frequency magnetron sputtering at 500°C. Dark current, spectral responsivity and pulse response were carried out for the devices with different finger pitches. All the photodetectors showed the peak responsivity at 330 nm and the ultraviolet-visible rejection ratio (R330 nm/R400 nm) is more than four orders of magnitude at 3 V bias. For the device with 2 μm finger pitch, the detectivity was calculated as 4.2×10¹¹ cm Hz^1/2/W at 330 nm. Furthermore, the transient response measurement for all devices revealed similar rise time of 10 ns. The 90%-10% fall times are 130 ns, 170 ns and 230 ns for the devices with different finger pitches of 2 μm, 5 μm and 10 μm, respectively.

Date Published: 3 March 2008
PDF: 8 pages
Proc. SPIE 6621, International Symposium on Photoelectronic Detection and Imaging 2007: Photoelectronic Imaging and Detection, 662116 (3 March 2008); doi: 10.1117/12.790770

Published in SPIE Proceedings Vol. 6621:
International Symposium on Photoelectronic Detection and Imaging 2007: Photoelectronic Imaging and Detection
Liwei Zhou, Editor(s)