247 nm solar-blind ultraviolet p-i-n photodetector

We describe solar-blind p-i-n photodetectors based on short period superlattices of AlN∕Al0.08Ga0.92N. The devices are grown using gas source molecular beam epitaxy with ammonia on transparent sapphire substrates. The cutoff wavelength for the device is 247nm. For diodes with 150μm diameter mesas and sidewall surfaces passivated in oxygen plasma, we obtain extremely low dark leakage current of ∼3pA∕cm2 and high zero-bias resistance of ∼6×1014Ω. At 10V reverse bias the observed responsivity is 62mA∕W.