Limiting Strain-Relaxation in III-Nitride Heterostructures by Substrate Patterning

A new method of improving performance of group-III nitride devices by limiting the strain-relaxation on crystal substrates.

The usefulness of group-III nitrides such as gallium nitride (GaN) and its alloys has been well established for its use in the fabrication of optoelectronic and high-powered electronic devices. Given recent trends in industry standards, it is desirable to produce ultra-bright LEDs and LDs in regions beyond the blue region and in the green region. The problem with producing LEDs and LDs in the green regions by epitaxy is due to the complications in producing high-quality, high-in-composition crystals. When high-in-composition crystal structures are grown on a strained substrate layer, this causes misfit dislocations which degrade device performance.

Researchers at the University of California, Santa Barbara have developed a new method of improving performance of group-III nitride devices by limiting the strain-relaxation on crystal substrates. Limiting the strain-relaxation on group-III nitride substrates is achieved through a novel process of patterning the substrate with a specialized film which reduces the pre-existing thread dislocations before growth of the subsequent layers. By reducing these pre-existing thread dislocations, less misfit dislocation will result during layer growth and will allow for the growth of thicker/higher in composition layers of III-nitride alloy epilayers.