Performance of metal-semiconductor-metal structured diamond deep-ultraviolet photodetector with a large active area

In this work, the uniformity is significantly improved of the photoresist film spinning-coated on the small-size diamond wafer by inlaying the diamond wafer into a 1-inch polytetrafluoroethylene substrate; consequently, the utilizable surface area of the diamond wafer is remarkably increased. As a result, the interdigital electrodes of 2.5 mm x 2.5 mm in dimension are prepared on the single crystal diamond (5 mm x 5 mm x 0.5 mm) and a metal-semiconductor-metal structured diamond deep-ultraviolet photodetector with a large active area of 3.093 mm(2) has been fabricated. Compared to the maximum values of the interdigital-typed intrinsic diamond deep-ultraviolet photodetectors, the active area is increased by more than six times, and the photocurrent reaches the order of milliampere, which is about two orders of magnitude larger. Meanwhile, the responsivity and external quantum efficiency are 56.3 A W-1 and 328, respectively, at 50 V bias under 3.125 mu W mm(-2) 213 nm illumination, and the corresponding mobility-lifetime product of the diamond wafer is 1.11 x 10(-5) cm(2) V-1. As the voltage continued to increase, which still maintained an upward trend and did not appear saturated; the corresponding responsivity is up to 275.9 A W-1 at 120 V. In addition, the ultraviolet-visible light discrimination ratio is 1.4 x 10(4) at 10 V, and the carrier transit time between interdigital electrodes is measured to be only about 1 ns (excited by a 213 nm pulse laser), which shows that the photodetector has an ultrafast response speed.