The optimized growth of AlN templates for back-illuminated AlGaN-based solar-blind ultraviolet photodetectors by MOCVD

In this paper, AlN templates with different mesothermal AlN (MT-AlN) interlayer deposition cycles are prepared via metal-organic chemical vapor deposition (MOCVD) at first. The influence of the MT-AlN interlayer on the crystalline quality of AlN templates has been carefully investigated. The results show that the MT-AlN interlayer played the role of providing a strain gradient to release the strain from AlN along the growth direction. The crystalline quality, surface morphology and residual compressive stress of AlN templates can be greatly optimized through introducing one MT-AlN interlayer cycle during the growth of HT-AlN. And then, a PIN structure back-illuminated AlGaN-based solar-blind ultraviolet photodetector (SUV-PD) is further designed, grown and fabricated based on the optimized AlN template. The SUV-PD exhibits a low dark current density, a bandpass spectral responsivity with a peak value of 0.15 A W-1 at 271 nm, corresponding to an EQE as high as 68.8%, and a response speed of 6.5 ns. These results strongly reflect the high quality of AlN templates prepared via inserting a MT-AlN interlayer based on a common growth method.