Demonstration of Spectral Selectivity of Efficient and Ultrafast GaN/AlGaN-Based Metal–Semiconductor–Metal Ultraviolet Photodiodes

Efficient and ultrafast (aluminum)-gallium-nitride-based metal–semiconductor–metal (
${\text{Al}}_{x}$
)
${\text{Ga}}_{{1}-{x}}\text{N}$
ultraviolet (UV) photodiodes (PDs) were implemented to investigate the spectral properties of GaN/AlGaN-based photodetectors. Al composition of the GaN templates was varied from 0% to 30% to demonstrate the impact of Al mole fraction on the cutoff wavelength of these UV PDs. Asymmetric metal contact electrodes were fabricated to optimize the external quantum efficiency without compromising their ultrafast photoresponse. The best performing devices exhibited a peak response of 4 V and an oscilloscope limited temporal pulsewidth of 61 ps at a 20-V bias with a peak spectral responsivity of 36.5 mA/W at 280 nm.