A 250 nm high-performance AlGaN-based metal-semiconductor-metal deep ultraviolet detector

The present work reports a Al0.67Ga0.33N Metal-Semiconductor-Metal (MSM) detector with a high quantum efficiency (QE) by metal organic chemical vapor deposition (MOCVD) and Standard photolithography. As previously reported, the electrode spacing between the metal fingers of MSM detectors, annealing temperature, and electrode material affect the performance of detectors. Our work demonstrates a high QE detector by optimizing the electrode and annealing temperature. At 14 V bias, the ultraviolet-to-visible rejection ratio is measured as high as 1000. It is also found that the responsivity increases with the bias voltage. Due to the influence of the image force and tunnel effect, the QE exceeds 100 % and the responsivity reaches 4.24 A/W near 250 nm. The specific detectivity (D*) also reaches 1.32 x 1011 Jones. Compared with the literature, this is the highest QE of MSM devices with Ti electrodes on the AlGaN layer at this wavelength. This gain mechanism should be related to trapping photo carriers at the semiconductor/metal interface, image-force lowering of Schottky barrier height, and the expansion of the space charge layer (SCR).