Investigation of AlGaN-Delta--GaN Based UV Photodiodes in a
Metal--Semiconductor--Metal Configuration for Efficient and Fast Solar
Blind UV Sensing
Abstract
Metal–semiconductor–metal (MSM) configuration UV photodiodes (PD’s)
were designed and fabricated on an AlGaN/GaN–based substrate for
efficient and ultrafast UV detection. The purpose was to investigate the
feasibility of obtaining efficient and ultrafast temporal response from
these devices in the UV given the challenges associated with the
formation of Schottky contacts on laterally oriented AlGaN/GaN thin
films. Two sets of devices were implemented using Pt and Au as metal
contacts with 5-mm finger width, 5-mm finger spacing, and
a 50-mm ´ 50-mm active area. Spectral and voltage bias
studies were done to establish the spectral profile and the effect of
bias voltage on the responsivity of the detectors at 265 nm. The best
vertical MSM PD’s produced 0.6-A/W responsivity under 10-V bias voltage
at 265 nm. Peak spectral responsivities were recorded as 1.35 A/W and
1.25 A/W at 240 nm for Pt and Au PD’s respectively.