Large Wavelength Response to Pressure Enabled in InGaN/GaN Microcrystal LEDs with 3D Architectures

Abstract

Optical detection of pressure has the advantage of direct and dynamic indication of the pressure distribution with a high spatial resolution. In this study, microcrystal (mu-crystal) light-emitting diodes (LEDs) that can exhibit an unprecedented large wavelength response to pressure are demonstrated. As a key strategy, three-dimensional InGaN/GaN mu-crystals are engineered to have a hollow core and multiple facets with different multiple quantum well (MQW) structures. The unique structure allows pressure-sensitive modulation of the dominantly emitting MQWs, resulting in an anomalously large change of similar to 50 nm in the ultimate emission wavelength under an external stress of 8 MPa. The underlying mechanism is elucidated via finite-element analysis of the strain development in the mu-crystals and the corresponding piezo-potentials. The results of the study suggest a new capability for dynamic color mapping of the pressure distribution with a high spatial resolution.