High quality GaN tetrapodal structures hetero-integrated on 3D Si surfaces

Abstract

Gallium nitride (GaN) light-emitting diodes (LEDs) on silicon (Si) substrates have been highlighted due to the potentials to achieve significant cost reduction, effective thermal management, and highly directional light emission, by replacing the conventional sapphire substrates with the opportunities to adopt the well-established Si-based semiconducting technologies. However, large mismatch of physical properties between Si and GaN considerably lowers the material quality of GaN and the corresponding device performances. Herein, we employ three-dimensional faceted Si surfaces (3D faceted Si) to effectively release the generated strain energy during the hetero-epitaxial growth of GaN on Si for fabricating high performance GaN-on-Si LEDs. The resulting outcome not only includes the unique morphology of 3D tetrapodal GaN layers on 3D faceted Si to form space-filling arrays for efficient device utilization, but also contains the excellent material quality of the hetero-integrated GaN layers, comparable to that grown on planar sapphire substrates. Consequently, those 3D tetrapodal GaN-on-Si LEDs exhibit the excellent light extraction characteristics due to their shapes to effectively suppress total internal reflection of generated light. In addition, the anisotropic formation of active layers in the 3D tetrapodal GaN-on-Si LEDs performs multi-color emission characteristics with tunable color capabilities.