A scalable, flexible and transparent GaN based heterojunction piezoelectric nanogenerator for bending, air-flow and vibration energy harvesting

•A novel fabrication of GaN based heterojunction flexible piezoelectric generator.•Piezoelectricity from vibrations, finger force, air-flow, and cyclic agitation.•High electrical energy generation from ambient vibrations.•High output voltages by suppressing internal screening and junction screening.