A Monolithic Quantum‐Dot/AlGaN Phototransistor Breaking the UV–NIR Sensitivity Trade‐off for Ultrasensitive Dual‐Band Detection

ABSTRACT

Simultaneous detection of solar‐blind ultraviolet (UVC) and second near‐infrared (NIR‐II) light is highly desirable for advanced optoelectronic functions like all‐weather vision. However, monolithic integration of these two bands is hindered by a fundamental material incompatibility, imposing a fundamental trade‐off between UVC and NIR sensitivity. Here, a monolithic dual‐band phototransistor is demonstrated​ by integrating a PbS colloidal quantum dot (CQD) NIR‐II sensitizer with a polarization‐engineered AlGaN/AlN UVC channel. A built‐in virtual photogate, arising from strong polarization fields, enables ultrahigh photogating gain in both bands without compromising speed or spectral purity. The device achieves record room‐temperature performance: a responsivity of 7.9 × 10 ⁶ A/W and a specific detectivity of 1.5 × 10 ¹⁸ Jones at 260 nm, together with 1.1 × 10 ³ A/W and 2.0 × 10 ¹⁴ Jones at 1550 nm. An ultralow optical crosstalk below −30 dB and ambient stability exceeding 200 days are demonstrated. The detector successfully performs dual‐band imaging and optical communication under nanowatt‐level illumination. This work presents a versatile materials platform for high‐performance, multispectral optoelectronics.