Intensity-Stable Wavelength Tuning in InGaN/GaN Multiple Quantum Wells

Abstract

Dynamic tuning of emission from III-nitride multiple quantum wells (MQWs) without significant intensity variation is a highly desirable feature as the emission wavelength from MQWs is generally fixed. This work demonstrates a three-terminal InGaN/GaN field-effect light-emitting diode (FE-LED) that exploits an external electric field to manipulate the band structure in highly strained MQWs for achieving intrinsic and dynamic wavelength tuning. A field-effect electrode, isolated from the p-GaN layer with a SiO2 passivation layer, is applied to change the emission wavelength independently from the driving current. Device optimization, including a reduction in dimensions of the device and the use of interdigitated p- and field electrodes with 3 μm wide fingers and spacings, enhances the field penetration and tuning efficiency. For a 50 μm diameter circular FE-LED, an applied field voltage of 40 V produces a spectral blue-shift of up to 11 nm. Under a constant current injection of 0.5 mA, the peak wavelength shifts from 599 to 588 nm, while the variation of normalized electroluminescence intensity remains within 10.6%, demonstrating intensity-stable color tuning. Finite-element Poisson–Schrödinger simulations of the band structure reproduce the measured spectral shifts and reveal that the external field primarily induces long-range band bending across the MQW region, effectively increasing the transition energy without significantly modifying the intrawell polarization tilt. The proposed FE-LED architecture, which is compatible with standard microfabrication processes, enables practical and intrinsic wavelength tuning and is suitable for applications requiring multiwavelength emission on-chip photonic systems.