Plasma modification induced interface engineering enhanced GaN UV photodetectors with ultrahigh performance and bias-tuned selective response

Deficient assembly of interfaces often results in considerable leakage current and compromised device performance, therefore, interface engineering strategy has emerged as a crucial aspect of device fabrication. In this work, the metal/semiconductor (M/S) interface was modified by single-sided plasma etching to fabricate an asymmetric M/S contact GaN-based photodetector (PD). Compared to untreated GaN-based PD, the GaN-based PD with interface engineering exhibits superior performance with an ultrahigh light-dark current ratio of 9.35 × 10⁹ and a high detectivity of 5.64 × 10¹⁷ Jones. Even considering noise effects, the detectivity value remains high at ∼10¹⁶ Jones, which is comparable to photomultiplier tubes. The performance improvement is attributed to the passivation of GaN interface dangling bonds by plasma treatment, while the localized N vacancies induced by etching act as shallow donor energy levels in the GaN energy band structure, reducing the barrier height of the interface and increasing the transport efficiency of charge carriers. In addition, by affecting the depletion layer width of the M/S interface, the device gains a bias-tuned selective response (UVC, UV-C to A, UVA waveband), which can meet various application requirements. Consequently, intentionally introducing local defects via interface engineering is an efficient strategy to optimize device performance while serving as a reference for future device design.