Self-powered p/Ga2O3/GaN p–i–n ultraviolet photodetector with a composite material made of polypyrrole (PPy) and nitrogen-doped graphene (PGr) as the P-region

A PPy/PGr/Ga2O3/GaN p–i–n heterojunction ultraviolet photodetector (UV PD) with polypyrrole (PPy) and nitrogen-doped graphene (PGr) combined as the p-region was fabricated, in which β-Ga2O3 was synthesized by substituting oxygen atoms for nitrogen atoms in the top layer of the GaN matrix at high temperature. In the self-powered mode, the device exhibits bimodal responses in the UVC–UVA bands. Compared with the single-peak response of the previously reported Ga2O3/GaN structure, the spectral response range has been greatly extended. In the UVC band, the responsivity reaches 36.4 mA/W, which is 21.4 times that of the unmodified device. The detectivity was improved to 1.5 × 1011 Jones, showing an 11.3-fold enhancement. It also exhibits fast photoresponse characteristics (rise/fall times of 0.09/10.8 ms, respectively). The significant improvement of device performance is mainly attributed to the effective modification of carrier transport by PPy and PGr, which not only increases the built-in electric field at the Ga2O3/GaN interface but also significantly suppresses carrier recombination. The design strategy proposed in this study, based on the synergistic incorporation of organic polymers and two-dimensional materials, provides new ideas and technical references for the development of ultraviolet photodetectors with high sensitivity and broad and fast spectral response.