High gain, large area, and solar blind avalanche photodiodes based on Al-rich AlGaN grown on AlN substrates
Pramod Reddy, M. Hayden Breckenridge, Qiang Guo, Andrew Klump, Dolar Khachariya, Spyridon Pavlidis, Will Mecouch, Seiji Mita, Baxter Moody, James Tweedie, Ronny Kirste, E. Kohn, Ramón Collazo, Zlatko Sitar
Abstract
We demonstrate large area (25 000 μm2) Al-rich AlGaN-based avalanche photodiodes (APDs) grown on single crystal AlN substrates operating with differential (the difference in photocurrent and dark current) signal gain of 100 000 at 90 pW (<1 μW cm−2) illumination with very low dark currents <0.1 pA at room temperature under ambient light. The high gain in large area AlGaN APDs is attributed to a high breakdown voltage at 340 V, corresponding to very high breakdown fields ∼9 MV cm−1 as a consequence of low threading and screw dislocation densities < 103 cm−2. The maximum charge collection efficiency of 30% was determined at 255 nm, corresponding to the bandgap of Al0.65Ga0.35N, with a response of 0.06 A/W. No response was detected for λ > 280 nm, establishing solar blindness of the device.