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

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.

Automated summary

This study demonstrates the preparation of freestanding InGaN/GaN quantum-wells membrane and optimization of the emission intensity and polarization characteristics in vertical devices by introducing the Piezo-phototronic effect. Under external straining, the EL intensity of the LED is significantly increased, and the polarization ratio of emission light is adjusted. The polarization ratio of photoresponse current in PD also shows significant changes under different strain conditions.