Performance improvement of GaN-based metal–semiconductor–metal photodiodes grown on Si(111) substrate by thermal cycle annealing process

A simple thermal cycle annealing (TCA) process was used to improve the quality of GaN grown on a Si substrate. The X-ray diffraction (XRD) and etch pit density (EPD) results revealed that using more process cycles, the defect density cannot be further reduced. However, the performance of GaN-based metal?semiconductor?metal (MSM) photodiodes (PDs) prepared on Si substrates showed significant improvement. With a two-cycle TCA process, it is found that the dark current of the device was only 1.46 ? 10?11 A, and the photo-to-dark-current contrast ratio was about 1.33 ? 105 at 5 V. Also, the UV/visible rejection ratios can reach as high as 1077.