Intelligent Ultraviolet Sensor Composed of GaN-Based Photodiode and N-Channel Metal Oxide Semiconductor Si-Charge Transfer Type Signal Processor

Abstract

Au/n-GaN Schottky barrier diode combined with Si-charge transfer type signal processor was investigated to realize intelligent UV sensors with low noise and high sensitivity. A 10-nm-thick Au was used for the semitransparent Schottky contact. The dark current–voltage characteristic of the Schottky barrier diode exhibited the ideal factor of 1.28 and barrier height of 1.1 eV. The sensitivity of 26.3 mA/W was obtained at a wavelength of 296 nm for 12 µW/mm2 UV irradiation power. Furthermore, the Au/n-GaN Schottky barrier diode was connected with the Si-charge transfer type signal processor to examine the effectiveness of the combined device for a UV detector. The processor was driven by a programmable function generator. Using the open-circuit voltage Voc as the input signal, 350 mV output was achieved in a single integration cycle. The signal from the Schottky barrier diode was successfully amplified by accumulation operation of the Si-charge transfer type signal processor.