Rapid Response Solar Blind Deep UV Photodetector with High Detectivity Based On Graphene:N/βGa2 O3 :N/GaN p-i-n Heterojunction Fabricated by a Reversed Substitution Growth Method.

Abstract

This work reports a high-detectivity solar-blind deep ultraviolet photodetector with a fast response speed, based on a nitrogen-doped graphene/βGa2 O3 /GaN p-i-n heterojunction. The i layer of βGa2 O3 with a Fermi level lower than the central level of the forbidden band of 0.2eV is obtained by reversed substitution growth with oxygen replacing nitrogen in the GaN matrix, indicating the majority carrier is hole. X-ray diffractometershows that the transformation of GaN into βGa2 O3 with (-201) preferred orientation at temperature above 900°C in an oxygen ambient. The heterojunction shows enhanced self-powered solar blind detection ability with a response time of 3.2µs (rise)/0.02ms (delay) and a detectivity exceeding 1012 Jones. Under a reverse bias of -5V, the photoresponsivity is 8.3 A W-1 with a high Ilight /Idark ratio of over 106 and a detectivity of ≈9 × 1014 Jones. The excellent performance of the device is attributed to 1) the continuous conduction band without a potential energy barrier, 2) the larger built-in potential in the heterojunction because of the downward shift of Fermi energy level in β-Ga2 O3 , and 3) an enhanced built-in electric field in the βGa2 O3 due to introducing p-type graphene with a high hole concentration of up to ≈1020 cm-3 .