Development of highly-sensitive ultraviolet sensing method using diamond

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The purpose of this project is to develop a highly-sensitive ultraviolet light sensing method using diamond semiconductor as deep-UV (DUV) photodetector with response energy larger than 4.4 eV. For this purpose, Schottky photodiode and metal-semiconductor-metal (MSM) diode were fabricated. We developed thermally stable, highly sensitive Schottky-type photodiode for the first time by using thermally stable transition metal carbide and nitride Schottky contacts. The results obtained for three years are as follows.(1)The Schottky photodiode with the transition metal carbide, WC, Schottky contact and annealed Ti/WC Ohmic contact was developed. The discrimination ratio between the DUV (220 nm) and visible light (630 nm) was as large as 10^6. The photoresponse properties of the photodiode was almost unchanged after thermal annealing up to 550 C for 3 h.(2)The Schottky photodiode with the transition metal nitride, HfN, Schottky contact and annealed Ti/WC Ohmic contact was developed. This photodiode showed the high speed response time shorter than 0.3 s and the discrimination ratio between the DUV and visible light of 10^6 and simultaneously revealed the thermal stability up to 500 C.(3)In order to apply the diamond sensor to the flame sensor, fully-packaged and bonded photodiode devices were fabricated. In corroboration with ANTEC Co.,the flame detection/alarm system using the diamond DUV sensor was demonstrated for the first time.