Strain-induced polarization modulation at GaN/Ti interface for flexible thin-film sensor

We have presented an effective piezoelectric polarized interface modulation at GaN/Ti Schottky structure and fabricated a flexible GaN-based sensor using double-transfer method. Chemical etching of Ni sacrificial layer is proved to remove the temporary substrate without metal electrodes damages. The fabricated flexible GaN-based sensor with top and bottom Ti metal Schottky contact exhibits current on/off characteristic under external strain, whose current shows a 53.9% reduction by 2.3% tensile strain and a 67.8% enhancement by -2.3% compressive strain at 5V bias voltage. It is found that the light/dark current ratio in the GaN/Ti Schottky junction significantly increases near zero-bias voltage under 2.3% tensile strain, probably indicating the enhanced built-in piezoelectric polarized field at the interface. This work promotes the study of flexible sensor based on wurtzite III-V nitrides for wearable electronics and optoelectronics.