Innovative all-silicon based a-SiNx:O/c-Si heterostructure solar-blind photodetector with both high responsivity and fast response speed

Abstract

The photoresponsivity and response speed are two key figures of merit for the photodetector (PD). According to the previous reports, there is an inherent contradiction between high photoresponsivity and fast response speed in normal photoconductive-type PDs. Facing the challenge of coordinating this inherent contradiction, we propose an innovative design idea, which employs a luminescent wide-bandgap (WBG) amorphous oxynitride (a-SiNx:O) film as an absorption layer combining with monocrystalline silicon (c-Si) as a carrier transport layer, to construct an all-silicon based a-SiNx:O/c-Si heterostructure photoconductive-type solar-blind photodetector (SBPD). Benefiting from the built-in electric field in the a-SiNx:O/c-Si heterojunction and good passivation at the SiNx:O/Si interface, the photogenerated carriers in the a-SiNx:O layer can be injected into the c-Si layer, which separates the carrier transport process from the carrier photogeneration/recombination process in the different layers. Since the transport process of injected carriers in the c-Si layer is much faster than their recombination process, the detector yields a large photoconductive gain, thus overcoming the above-mentioned inherent contradiction in normal photoconductive-type PDs, where both the defect-related carrier photogeneration/recombination process and carrier transport process occur in the same active layer. The designed SBPDs exhibit highlighted performance with both the high responsivity (R) of 4 × 103 A/W at 225 nm and the fast response speed of 4.3 µs. Compared to most other WBG semiconductor SBPDs, e.g., AlxGa1−xN, MgxZn1−xO, Ga2O3, and diamond, the advantages of the a-SiNx:O/c-Si heterostructure SBPD lie not only in adopting economic Si-based materials but also in manufacturing processes compatible with mature CMOS technology, thereby rendering it preferable for the development of cost-effective large-area SBPD arrays.