Uniform and Reliable GaN p-i-n Ultraviolet Avalanche Photodiode Arrays

GaN p-i-n ultraviolet avalanche photodiodes (UV-APDs) were fabricated from epitaxial structures grown on low-dislocation-density free-standing GaN substrates to form 4x4 UV-APD arrays with a device size of 75x75 mu m(2). The devices in the UV-APD array showed a uniform and reliable distribution of breakdown voltage (V-BR) and leakage current density. The average VBR of the 16 devices in one of the UV-APD arrays was 96 +/- 0.6 V, and the average dark current density (J(R_Dark)) and photocurrent density (J(R_Photo)) were measured to be (6.5 +/- 1.8) x 10(-7) and (5.7 +/- 1.1) x10(-6) A/cm(2) at the reverse bias voltage of V-R = 48 V (50% of the average onset point of V-BR), respectively. The reliable device performance was confirmed by performing multiple reverse bias I-V scans for the selected devices in the UV-APD array. We also observed the significantly enhanced spectral responsivity from the 142 to 5485 mA/W due to the strong carrier impact ionization at high reverse bias.