Rapid Response Solar Blind Deep UV Photodetector with High Detectivity Based On Graphene:N/βGa 2 O 3 :N/GaN p-i-n Heterojunction Fabricated by a Reversed Substitution Growth Method.

This work reports a high-detectivity solar-blind deep ultraviolet photodetector with a fast response speed, based on a nitrogen-doped graphene/βGa 2 O 3 /GaN p-i-n heterojunction. The i layer of βGa 2 O 3 with a Fermi level lower than the central level of the forbidden band of 0.2 eV 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 βGa 2 O 3 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 3.2 µs (rise)/0.02 ms (delay) and a detectivity exceeding 10 12 Jones. Under a reverse bias of -5 V, the photoresponsivity is 8.3 A W -1 with a high I light /I dark ratio of over 10 6 and a detectivity of ≈9 × 10 14 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-Ga 2 O 3 , and 3) an enhanced built-in electric field in the βGa 2 O 3 due to introducing p-type graphene with a high hole concentration of up to ≈10 20 cm -3 .