Uniform and Reliable GaN <italic>p-i-n</italic> Ultraviolet Avalanche Photodiode Arrays

Abstract

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 4 × 4 UV-APD arrays with a device size of 75 × 75 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The devices in the UV-APD array showed a uniform and reliable distribution of breakdown voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> ) and leakage current density. The average V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> of the 16 devices in one of the UV-APD arrays was 96±0.6 V, and the average dark current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_Dark</sub> ) and photocurrent density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_Photo</sub> ) were measured to be (6.5±1.8)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> and (5.7±1.1)×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the reverse bias voltage of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> = 48 V (50% of the average onset point of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> ), 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.