Visible and near-infrared photodetector on chemically vapor deposited diamond

Abstract

A photodetector of the visible and near infrared wavelength ranges based on chemically vapor deposited (CVD) boron-doped diamond is fabricated and tested. The principle of its operation is based on the creation of holes by incident radiation not in a CVD diamond film itself, but in an adjoining bimetal Cr/Au layer. The latter serves simultaneously as one of the Schottky contacts with an external circuit. Due to small thickness of this layer in the order of 10 nm the generated holes do not have enough time to recombine with electrons because of diffusion in the CVD diamond film. There the holes are accelerated by the electric field of a hole depletion region and create a photocurrent. For optimized boron doping profile of the CVD diamond film the photodetector Volt-Watt sensitivity in the order of 1 mV/(W/cm2) at wavelength 445 nm and 0.1 mV/(W/cm2) at 532 nm was measured. For a constant forward bias voltage 2.5 V its Ampere-Watt sensitivity at 445 nm is 0.7 A/W. For zero bias voltage this figure is 5 ⋅ 10−5 A/W at 445 nm, 3 ⋅ 10−6 A/W at 532 nm, and 1.8 ⋅ 10−7 A/W at 1.06 μm. The photodetector time response was measured in the current mode at 532 nm. It is in the order of 600 ns without a bias voltage and 200 ns with a constant reverse bias voltage 2.5 V.