Optimized performances in InGaN/GaN quantum-well membrane based vertical optoelectronics by the Piezo-phototronic effect

Abstract

In this work, by conducting selective electrochemical (EC) etching of the sapphire based nitrides epitaxial film, freestanding InGaN/GaN quantum-wells (QWs) membrane was firstly and specifically prepared. InGaN/GaN QWs based device with vertical geometry were then fabricated using the membranes, which can work either as a light-emitting diode (LED) or as a photodetector (PD). The emission intensity and polarization characteristics of vertical devices are optimized by introducing the Piezo-phototronic effect under external straining. Under a tensile strain of 2.04%, the relative electroluminescence (EL) intensity of the LED is increased by 183%, which is ascribed to the enhancement of carriers recombination arisen from the external-strain-induced Piezo-phototronic effect. And the polarization ratio of the emission light is increased or decreased by 135% and 56% under the tensile or compressive strain of 2.04%. For the PD working mode, the polarization ratio of photoresponse current is increased by 107% under the condition of 2.04% tensile strain, while it is reduced by 81% under compressive strain. The modulated polarization characteristics in the vertical devices were attributed to the adjustment in anisotropic optoelectronic properties of InGaN/GaN QWs. This work provides a novel method to fabricate vertical nitride optoelectronics and also presents a unique strategy to their optoelectronic performances.