Growth and characteristics of Ni-based Schottky-type AlxGa1−xN ultraviolet photodetectors with AlGaN∕GaN superlattices

We investigated the structural, optical, and electrical properties of Ni-based Schottky-type AlxGa1−xN ultraviolet (UV) photodetectors. Three different types of AlxGa1−xN∕GaN heterostructures were epitaxially grown on (0001) sapphire substrates by metalorganic chemical vapor deposition. We found that the insertion of Al0.2Ga0.8N∕GaN superlattices (SLs) improved the crystal quality of AlxGa1−xN∕GaN heterostructures from photoluminescence and x-ray diffraction experiments. As a result, AlxGa1−xN UV photodetectors with Al0.2Ga0.8N∕GaN SL layers showed superior device performance with lower turn-on voltage and higher responsivity compared to those without SLs. We obtained a dark current of 0.1 nA at −5V, a responsivity of 0.097A∕W at zero bias, and a specific detectivity of D*=8×1013cmHz1∕2W−1 at λ=290nm for AlxGa1−xN UV photodetectors with Al0.2Ga0.8N∕GaN SLs.