Ultraviolet Phototransistors on AlGaN/GaN Heterostructures

We report on the fabrication and characterization of phototransistors based on AlGaN/GaN heterostructure grown over 6H-SiC substrates. The device has two functions: as a high electron mobility transistor (HEMT) and an ultraviolet photodetector at the same time. As an HEMT, its maximum transconductance is 170mS/mm, while the minimum cutoff frequency f_T and the maximum oscillation frequency f_m are 19 and 35GHz, respectively. As a photodetector, the device is visible blind, with an ultraviolet/green contrast of three orders of magnitude, and a responsivity as high as 1700A/W at the wavelength of 362nm.