PROCEEDINGS ARTICLE | August 24, 2009
Proc. SPIE. 7381, International Symposium on Photoelectronic Detection and Imaging 2009: Material and Device Technology for Sensors
KEYWORDS: Semiconductors, Avalanche photodetectors, Ultraviolet radiation, Silicon, Gallium nitride, Ionization, Avalanche photodiodes, Silicon carbide, Heterojunctions, Ultraviolet detectors
GaN-based avalanche photodiodes (APDs) have become of increased interest in the UV detection arenas. However,
numerous material-, fabrication-, and design-related problems are exactly settled before GaN-based APDs can be
commercialized. In this study, we, first, discussed recent development of the GaN-based APDs. Then front- and
back-illumination (respectively realizing electron and hole initial impact-ionization) p-i-n heterostructure devices with
various mesa diameters were fabricated. The device with a diameter of 40 μm exhibited a multiplication gain of ~680, at
reverse bias of ~76 V corresponding to the magnitude of the electric field of ~ 3 MV/cm by experiment indicating and
simulation verifying. To confirm the origin of dark current under different reverse bias, the dark current-voltage
characteristic of various sized mesa devices were performed. The dark current could be linearly fitted to the device
diameter (or circumference) implied that the surface leakage along the mesa sidewall was the dominant component of the
dark current. At zero bias, the spectral peak responsivity reached ~ 0.14A/W for front illumination, and ~ 0.152A/W for
back illumination at a wavelength of 358 nm. The positive breakdown voltage coefficient from the
temperature-dependent current-voltage characteristics was 0.02 V/K.
