Scientists at the University of Hong Kong (HKU), led by Prof. Yang Lu, have successfully used mechanical stretching technology to dynamically control the emission color of GaN LEDs, from UV to blue light.
The researchers utilized micro-nano processing technology to fabricate single-crystalline GaN material into tiny bridge-like structures. Through precise mechanical stretching, the material achieved an elastic deformation of up to 6.8%, with a tensile strength of approximately 11 GPa. This demonstrates the extraordinary elastic deformation capability brought by the size effect, offering broad prospects for deep strain engineering.
The researchers observed that when the stretching degree reached 3.9%, a significant change in emission color was observed - the bandgap of GaN continuously redshifted from 3.41 eV to 3.08 eV, and the emission wavelength correspondingly shifted from the ultraviolet region into the visible light region. Under maximum strain conditions, the bandgap could be further reduced to 2.96 eV (wavelength shifting from approximately 365 nm to 420 nm).
To demonstrate the potential for practical device applications, the research team further designed and microfabricated a mechanically strain-fixed GaN device with a push-to-pull structure. By locking in a tensile strain of ~3%, the device successfully achieved a stable wavelength redshift from 363 to 371nm, maintaining the strained light emission state without requiring continuous external force, making this design more practical for applications.
