Tunable Near‐Infrared Photodetection Enabled by Plasmonic Effect in Er‐Doped GaAs

Abstract Localized surface plasmon resonance (LSPR)‐induced electron transfer presents a compelling strategy for enhancing and expanding the functionality of optoelectronic devices. This work demonstrates extended near‐infrared (NIR) photodetection in rare‐earth Er‐doped GaAs by leveraging the LSPR effect of semi‐metallic ErAs nanoparticles (NPs). High‐quality Er‐doped GaAs films, with two different structures, co‐deposited and superlattice, are grown by molecular beam epitaxy. LSPR‐enhanced absorption is confirmed using Fourier transform infrared spectroscopy and Maxwell–Garnett approximations. Finite element method simulations reveal significant local electric field enhancement near ErAs NPs and predict the tailorable photoresponse by manipulating the NP configurations. Consequently, tunable photodetection with extension to the critical 1.3 and 1.5 µm telecommunication bands, is achieved in PIN photodetectors using Er‐doped GaAs as the absorption layers. At room temperature, the photodetector with 0.2% ErAs achieves a peak responsivity of 5.8 mA W⁻¹ and detectivity of 3.73 × 10⁷ cm·Hz^1/2/W at −4.5 V, with a low dark current density of 2.19 × 10⁻⁴ A cm⁻² at −1V. These findings establish the potential of ErAs NPs for LSPR‐enhanced NIR photodetection and provide valuable insights into rare‐earth doped materials for high‐performance optoelectronic devices.