We have developed a thermally stable, deep-ultraviolet (DUV) photodiode using tungsten carbide (WC) Schottky and Ti/WC ohmic contacts for a boron-doped homoepitaxial p-diamond epilayer. Effects of thermal annealing in an argon ambient on the electrical and photoresponse properties were investigated. Annealing at temperatures up to 550°C improves the rectifying current-voltage characteristics, resulting in a dramatic enhancement of DUV responsivity at 220nm by a factor of 4×103. A blind ratio as large as 105 between DUV and visible light has been achieved at a reverse bias as small as 1V. Development of the thermally stable WC-based Schottky and ohmic contacts provides a route for stable operation of a diamond photodetector at high temperatures.

The development of efficient photodetectors (PDs) for ultraviolet (UV) light is of great importance for many applications. In the present paper, we propose a novel approach for boosting the performances of self-powered PDs. Visible-blind UV-A PDs have been built by combining a mesoporous TiO2 layer with a Spiro-OMeTAD layer. The nanostructured heterointerface has been engineered by inserting a self-assembled layer of organic modifiers. By choosing the 4-nitrobenzoic acid (NBA), the responsivity has been boosted by 70% compared to the pristine devices. It achieved 64 mA/W at 0 V bias, 380 nm and 1 mW.cm-2. The PD displayed a very high sensitivity (> 10 4), a fast response time (< 3ms), a high stability and repeatability. 4-chlorobenzoic acid, 4-methoxy benzoic acid, 4-nitro benzoic acid and βalanine surface modifier have been studied by a combined experimental and theoretical approach. Their dipole moment has been calculated. Their presence induces a step in the Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))