A GaN p–i–p–i–n Ultraviolet Avalanche Photodiode

A separated absorption and multiplication GaN p–i–p–i–n avalanche photo-diode (APD) with a 25 μm diameter mesa is proposed and demonstrated. Compared to the conventional p–i–n APD, the p–i–p–i–n structure reduces the probability of premature micro-plasma breakdown, raises the gain from 30 to 400 and reduces the work voltage from 93 to 48 V. The temperature test is set on p–i–p–i–n APDs, and the positive coefficient of 30 mV/K shows that avalanche breakdown happens in the devices. The peak responsivity of p–i–p–i–n APDs is 0.11 A/W under a wavelength of 358 nm.