Piezo-phototronic effect modulated performances of guest-substrate integrated p–i–n GaN ultraviolet detectors

Abstract

High quality freestanding p–i–n GaN UV photodiodes were successfully fabricated on flexible mica by using selective electrochemical (EC) etching and an In–Au (50 nm/50 nm) bonding layer, which is convenient and the thermal damage is low. By applying external strain along the c-axis orientation in i-GaN, the photoexcited electron–hole pairs in the p–i–n GaN UV photodiode can be significantly modulated by the piezo-phototronic effect. The responsivity (R) was increased by 73% and the response time was decreased to 0.50 ms/0.57 ms under a tensile strain of 0.36%. When subjected to 0.36% compressive stress, R can be reduced by 81% and the response time was prolonged to 2.0 ms/3.0 ms. This study opens a pathway for guest-substrate integrated p–i–n GaN ultraviolet detectors and provides fundamental support for synergistically improving the R and response speed of ultraviolet photo-sensing by the piezo-phototronic effect.