Voltage-Controlled Dual-Band Electroluminescence from In-Doped hBN/GaN Heterojunctions for Switchable UV–Visible Emission

Achieving efficient n-type doping in hexagonal boron nitride (hBN) remains a critical challenge for deep-UV optoelectronics. Here, we demonstrate voltage-controlled dual-band electroluminescence (EL) in In-doped hBN heterostructures epitaxially grown on p-GaN via magnetic sputtering. Precise In doping introduces mid-gap states enabling n-type conductivity (carrier density: 3.87 × 10¹⁸ cm^-3) and activates ultraviolet emission (332 nm, 378 nm) above 6 V bias in In-doped hBN. Simultaneously, the GaN region exhibits bias-dependent blue (447 nm, <14 V) and UV-violet (377 nm, > 14 V) emission with broad visible bands. First-principles calculations reveal that In substitution at B sites creates recombination centers, while unintentional defects in GaN drive yellow-blue transitions. The p-n heterojunction facilitates efficient carrier injection, enabling dynamic spectral tuning from UV to visible light. This work establishes a new paradigm for adaptive light sources in wide-bandgap semiconductors.