Dependence of electrical field and photoresponse on multiplication region thickness for GaN APDs

A visible-blind ultraviolet GaN back-illuminated avalanche photodiode with separate absorption and multiplication regions are simulated based on drift-diffusion equation. The current-voltage characteristics of the device have been numerically obtained. The result is in good agreement with the experimental data. It was found that the thickness of the multiplication layer is important to improve the electrical field profiles and spectral response characteristics. A peak responsivity of 106.5mA/W is achieved at 364 nm corresponding to the cutoff wavelength of GaN.