Design, fabrication and physical analysis of TiN/AlN deep UV photodiodes

Deep-ultraviolet solar-blind photodiodes based on high-quality AlN films grown on sapphire substrates with a metal-semiconductor-metal configuration were simulated and fabricated. The Schottky contact is based on TiN metallization. The material is characterized by the micro-Raman spectroscopy and x-ray diffraction technique. The detector presents an extremely low dark current of 100 fA at -100 V dc bias for large device area as high as 3.1 mm². It also exhibits a rejection ratio between 180 and 300 nm of three orders of magnitude with a very sharp cut-off wavelength at 203 nm (~6.1 eV). The simulation to optimize the photodiode topology is based on a 2D energy-balance model using the COMSOL® software. Simulation performed for different spacing for a given bias between electrodes show that a compromise must be found between the dark current and the responsivity for the optimization of the device performance. The measurement results are in good agreement with the model predictions.