Highly Sensitive Narrowband AlGaN Solar Blind Ultraviolet Photodetectors Using Polarization Induced Heterojunction Barrier
Zesheng Lv, Quan Wen, Yezhang Fang, Zhuoya Peng, Hao Jiang
Abstract
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-Al0.4 GaN/i-Al0.5GaN 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{7}\times {10} ^{{{17}}}\vphantom {{1}^{{1}^{{1}}}}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{{6}}}$ </tex-math></inline-formula> were obtained under wake light of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.45~\mu \text{W}$ </tex-math></inline-formula> /cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{-{2}}}$ </tex-math></inline-formula> . These results confirmed the feasibility of our proposed PHB-PD in highly sensitive and color-distinguishing photodetection.