Highly Sensitive Narrowband AlGaN Solar Blind Ultraviolet Photodetectors Using Polarization Induced Heterojunction Barrier

A highly sensitive narrowband solar-blind ultraviolet photodetector (PD) was fabricated using polarization induced heterojunction barrier (PHB) in an n-i-i-n type AlGaN structure. The i-Al _0.4 GaN/i-Al _0.5 GaN heterojunction is utilized to generate net negative interface polarization charges and strong polarization electric field, which can deplete the i-layers and lead to an effective interface barrier. Such a PHB can significantly hinder the carrier transport in the absence of irradiation, while localizing photogenerated holes under UV illumination, thereby lowering the barrier height and generating a high optical gain. On this basis, the top n-type injection layer and the bottom n-type transmission window layer are introduced to improve the current gain and achieve short-wavelength cutoff. The resulting PHB-PDs demonstrated a superhigh shot-noise-limited specific detectivity of 1.7×10 ¹⁷ jones at 7 V bias under 274-nm back illumination. Meanwhile, a bandpass spectral response with a linewidth of ~16 nm and an ultrahigh spectral rejection ratio over 10 ⁶ were obtained under wake light of ~0.45 μW/cm ^-2 . These results confirmed the feasibility of our proposed PHB-PD in highly sensitive and color-distinguishing photodetection.