UV detector based on InAlN/GaN-on-Si HEMT stack with photo-to-dark current ratio> 107

We demonstrate an InAlN/GaN-on-Si high electron mobility transistor based UV detector with a photo-to-dark current ratio of  >10⁷. The Ti/Al/Ni/Au metal stack was evaporated and thermal annealed rapidly for Ohmic contacts to the 2D electron gas (2DEG) at the InAlN/GaN interface, while the channel + barrier was recess etched to a depth of 20 nm to pinch-off the 2DEG between Source-Drain pads. A spectral responsivity (SR) of 32.9 A/W at 367 nm was measured at 5 V. A very high photo-to-dark current ratio of >10⁷ was measured at a bias of 20 V. The photo-to-dark current ratio at a fixed bias was found to be decreasing with an increase in the recess length of photodetectors. The fabricated devices were found to exhibit a UV-to-visible rejection ratio of >10³ with a low dark current of < 32 pA at 5 V. Transient measurements showed rise and fall times in the range of 3–4 ms. The gain mechanism was investigated, and carrier lifetimes were estimated which matched well with those reported elsewhere.