Low-noise photodetectors based on heterojunctions of AlGaN–GaN

We describe detailed current–voltage and noise measurements carried out on AlGaN–GaN heterojunction photodetectors. Dark current densities below 1×10−10 A/cm2 are measured at a bias level of −5 V, at room temperature. In diodes with a diameter of 50 μm, low leakage currents result in the zero-bias noise spectral density as low as 3.6×10−32 A2/Hz. Based on the combined electrical and noise measurements, we calculate room-temperature thermally limited specific detectivity greater than 2.4×1014 cm Hz1/2 W−1. Background-limited specific detectivity exceeds 3.5×1013 cm Hz1/2 W−1.