Improvements of transparent electrode materials for GaN metal-semiconductor-metal photodetectors

• Published in: Journal of materials science. Materials in electronics 2004-12, Vol.15 (12), p.793-796
• Main Authors: WUU, Dong-Sing, HSU, Shun-Chen, HORNG, Ray-Hua
• Format: Article
• Language: English
• Subjects: Applied sciences; Contact; Devices; Electrodes; Electronics; Exact sciences and technology; Gain; Gallium nitrides; Indium tin oxide; Optoelectronic devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Titanium; Titanium dioxide
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1023/B:JMSE.0000045301.37195.d7

Metal-semiconductor-metal (MSM) photodetectors based on GaN grown on (0 0 0 1) sapphire were fabricated and characterized. The responsivity of the Pt/GaN MSM device is low due to the blocking of incoming light by Pt electrodes. Although this problem can be partly solved by the transparent indium-tin oxide (ITO) contact, the range of operation voltage for ITO/GaN MSM devices is limited by the internal gain. Transparent multilayered electrode is proposed in this work by incorporating various intermediate layers (Ti, TiO^sub 2^, and Ti/TiO^sub 2^). The dark current of the ITO/TiO^sub 2^/GaN contact is two orders of magnitude lower than that of the ITO/Ti/GaN contact. The thin TiO^sub 2^ barrier also contributes the lower responsivity of the ITO/TiO^sub 2^/GaN structure. By introducing a thin Ti/TiO^sub 2^ interlayer at the ITO-GaN interface, a significant decrease in the dark current and an increase in responsivity can be achieved simultaneously. The photo-to-dark current contrast can reach 6×l0^sup 5^, and the responsivity shows no discernible internal gain under a bias between 2.5 and 7.5 V.[PUBLICATION ABSTRACT]