The piezotronic effect in InGaN/GaN quantum-well based microwire for ultrasensitive strain sensor

Abstract

By introducing external mechanical strain, the carriers transport of certain semiconductors with non-centrosymmetric structure would be modulated, which is referred to the piezotronic effect. Herein, a piezotronic strain sensor with ultrahigh sensitivity based on InGaN/GaN multiple quantum-well heterojunction microwire (MQWH-MW) was designed. The InGaN/GaN MQWH-MW orientated along a-axis was directly obtained by conductivity-selective electronchemical (EC) etching of epitaxial film on sapphire. The strain sensor was fabricated into a back-to-back Schottky junction. The gauge factor of the fabricated strain sensor reaches over 2000 when applying 0.55% tensile strain under +0.4 V external bias. A theoretical analysis of energy band in the MQWH-MW based strain sensor is proposed to explain the observed result. Theoretical simulations about conduction band energy profiles and electron concentration of electron accumulation region (EAR) are performed and presented to systematically illustrate and confirm the proposed working mechanisms. This work demonstrates a promising approach to design and fabricate strain nanosensors with high sensitivety.