Metal-semiconductor-metal ultraviolet photodetectors directly fabricated on semi-insulating GaN:Fe template grown by hydride vapor phase epitaxy

• MSM photodetectors are directly fabricated on Fe-doped semi-insulating HVPE GaN template.
• The photodetector exhibits low dark current and acceptable UV-to-visible rejection ratio.
• The high-density defect states within the GaN:Fe layer have a strong influence on the performance of the photodetectors.

In this work, metal-semiconductor-metal ultraviolet (UV) photodetectors (PDs) are directly fabricated on Fe-doped semi-insulating GaN template grown by hydride vapor phase epitaxy. Under 20 V bias, the PD exhibits a room temperature low dark current of <2.5 pA, a UV-to-visible rejection ratio of up to 1 × 102 and a corresponding maximum quantum efficiency of ∼10%. At higher temperature, both the photo-current and dark current of the PD increase, and a reduced UV-to-visible rejection ratio is observed. A temporal response and recovery time of less than 2 ms is obtained for the PD, nevertheless its photocurrent is found to decrease continuously under stable UV illumination. There is evidence that the high-density trap states and recombination centers within the GaN:Fe layer have a strong influence on the photo-response characteristics of the PDs. This study provides a possible route to fabricate low cost GaN-based UV PDs with reasonable performance.