Back-illuminated Al_<i>x</i>Ga_1−<i>x</i>N-based dual-band solar-blind ultraviolet photodetectors

Abstract

Back-illuminated AlxGa1−xN-based dual-band solar-blind ultraviolet (UV) photodetectors (PDs) are realized by a three-terminal n—i–p–i–n heterojunction structure which is grown on sapphire substrate by metal organic chemical vapor deposition (MOCVD). The two p—i—n junctions contained in the heterojunction structure can work separately and independently. Working in the photovoltaic mode, the PDs display peak responsivity of ∼10.8 mA/W at 242 nm and ∼5.0 mA/W at 257 nm, respectively. The two junctions with different size, whose diameters are 500 μm and 800 μm, exhibit almost the same leakage current of ∼1.3 × 10−9 A at a reverse bias of 10 V. Therefore, dark current densities of the two junctions are close to 6.6 × 10−7 A/cm2 and 2.6 × 10−7 A/cm2 at −10 V respectively.