Modulation of carrier transport in bipolar response BDD/SnO₂ p⁺-n heterojunction UV photodetectors

A unique band-to-band tunneling (BTBT) phenomenon has been discovered in heavily boron-doped diamond (BDD)/SnO₂ p⁺-n heterojunctions. This phenomenon can be modulated by varying the bias voltage, changing the thickness of the SnO₂ film, and adjusting the power density of incident UV light. The near-broken-gap band alignment of the BDD/SnO₂ heterojunction and the existence of electrons in degenerate states in the valence band of BDD are the key to achieving BTBT. Moreover, BDD/SnO₂ p⁺-n heterojunction UV photodetectors (PDs) prepared by radio-frequency magnetron sputtering exhibit a binary photoresponse, large open-circuit voltage (V_oc-l), and high photo/dark current ratio (I_p/I_d). Those behaviors can be produced through periodic on/off UV light irradiation and by changing tunneling, drift, and thermionic emission currents. Our work, which is the first to achieve a binary photoresponse by modulating BTBT in BDD/SnO₂ heterojunctions, demonstrates the feasibility of extending BTBT theory to logical optoelectronic devices.