AlGaN/GaN Double-Channel Ultraviolet Photodetector With Polarization-Enhanced Photoresponsivity

In this work, an ultraviolet photodetector (UV PD) based on an AlGaN/GaN double-channel (DC) heterostructure is demonstrated. The carriers in both channels are partially depleted by a recessed trench to suppress the dark current. A high photoresponsivity of ${2}.{6}{\times }{10}^{\mathbf {{4}}}$ A/W is realized in the DC PD under 365-nm light illumination even with a low intensity of 3.8 $\mu $ W/ ${\mathrm {cm}}^{\mathbf {{2}}}$ , which is ~30 times higher than that of a single-channel (SC) counterpart. Moreover, a high specific detectivity of ${3}.{4}{\times }{10} ^{\mathbf {{15}}}$ cm $\cdot $ ${\mathrm {Hz}}^{\mathsf {rac{{1}}{{2}}}}$ /W and a relatively short decay time constant of ~2.3 ms have been achieved in the DC PD. The high photoresponsivity is possibly correlated with the spatial separation of the photogenerated carriers under the internal polarization field at the dual AlGaN/GaN heterointerface, as well as the photo-induced leakage current across the recessed trench. The GaN-based DC PD and the mechanism analysis in this work can provide valuable insights towards enhanced photoresponsivity especially for weak-light detection.