Work function engineering of MXene contacts for high-performance, self-powered AlGaN solar-blind photodetectors

AlGaN-based solar-blind UV photodetectors are crucial for critical applications but suffer from Fermi-level pinning that leads to high dark current. Constructing a high-barrier heterojunction interface effectively suppresses dark current, yet controlling the AlGaN/two-dimensional material barrier via work function modulation remains challenging. Here, we tailor the work function of MXene (3.7–4.6 eV) through surface oxidation to fabricate self-powered MXene/AlGaN van der Waals photodetectors. By alleviating Fermi-level pinning and forming a deep-depletion barrier, the device exhibits a suppression of dark current by nearly four orders of magnitude at 0 V (10⁻¹⁴ A regime). Consequently, the device achieves a high responsivity of 15 mA/W and a specific detectivity of 2 × 10¹¹ Jones at 280 nm, accompanied by a rapid response time of 0.66 ms. This work validates work function engineering as a potent strategy for optimizing interface energetics and boosting the performance of wide-bandgap optoelectronics.