The unipolar photocurrent in conventional photodiodes (PDs) based on photovoltaic effect limits the output modes and potential versatility of these devices in photodetection. Bipolar photodiodes with photocurrent switching are emerging as a promising solution for obtaining photoelectric devices with unique and attractive functions, such as optical logic operation. Here, we design an all-solid-state chip-scale ultraviolet (UV) PD based on a hybrid GaN heterojunction with engineered bipolar polarized electric field. By introducing the polarization-induced photocurrent switching effect, the photocurrent direction can be switched in response to the wavelength of incident light at 0 V bias. In particular, the photocurrent direction exhibits negative when the irradiation wavelength is less than 315 nm, but positive when the wavelength is longer than 315 nm. The device shows a responsivity of up to −6.7 mA/W at 300 nm and 5.3 mA/W at 340 nm, respectively. In particular, three special logic gates in response to different dual UV light inputs are demonstrated via a single bipolar PD, which may be beneficial for future multifunctional UV photonic integrated devices and systems.

Deep ultraviolet (DUV) phototransistors are key integral of optoelectronics bearing a wide spectrum of applications in flame sensor, military detector, oil spill detection, biological sensor, and artificial intelligence fields. In order to further improve the responsivity of UV photodetectors based on β-Ga₂O₃, in present work, high-performance β-Ga₂O₃ phototransistors with local back-gate structure were experimentally demonstrated. The phototransistor shows excellent DUV photoelectrical performance with a high responsivity of 1.01 × 10⁷ A/W, a high external quantum efficiency of 5.02 × 10⁹%, a sensitive detectivity of 2.98 × 10¹⁵ Jones, and a fast rise time of 0.2 s under 250 nm illumination. Besides, first-principles calculations reveal the decent stability of β-Ga₂O₃ nanosheet against oxidation and humidity without significant performance degradations. Additionally, the hexagonal boron nitride (h-BN)/β-Ga₂O₃ phototransistor can behave as a photonic synapse with ultralow power consumption of ~ 9.6 fJ per spike, which shows its potential for neuromorphic computing tasks such as facial recognition. This β-Ga₂O₃ phototransistor will provide a perspective for the next generation optoelectrical systems.