Multicolor Emission in Indium-Doped Amorphous Boron Nitride Integrated on Silicon for Self-Biased and High-Speed Photodetection

Boron nitride (BN), as an emergent wide-bandgap material, is gaining considerable attention as a solid-state deep ultraviolet source and quantum emitter from the ultraviolet to the near-infrared spectral ranges. However, studies of the defect structure of BN and efforts at scalable BN emitters in photonic devices are limited. Controlling the BN doping is of particular interest in view of the light emission of defects. Here, it is demonstrated for the first time that doping amorphous BN (a-BN) with indium (In) shows luminescence spectra tuning from blue to red light, and only 765 nm (1.63 eV) light is dominant when more In content is introduced. The visible light emission is found to be the transition between the defect center of In_N (a substitutional In of nitrogen) and O_NV_B (a substitutional oxygen with an adjacent boron vacancy). While O_NV_B is identified experimentally in accordance with previous theoretical assumptions, and is optically accessible with a zero-phonon line (ZPL) of about 1.63 eV with increasing In proportion. Moreover, the heterogeneous integration of synthesized In-doped a-BN in silicon platforms is demonstrated by the realization of a 700-1000 nm broadband photodetector. These devices operate self-biased at room temperature and show a high photoresponsivity of ∼1.5 A/W (at 980 nm with -2 V bias), a quick response time of ∼90 μs, and a detectivity of 1.02 × 10⁹ cm·Hz^1/2/W. This work fundamentally contributes to establishing infrared detection by doping a-BN materials in heterojunctions with Si, at the forefront of infrared optoelectronics.