Fabrication of a 2 inch free standing porous GaN crystal film and application in the growth of relaxed crack-free thick GaN

Abstract

A porous template has the function of relieving the stress of epitaxially grown GaN crystals and blocking dislocations. In this study, a 2 inch self-standing porous GaN crystal film was fabricated for the first time by a simple high-temperature annealing method. The influence of different annealing temperatures on the porous structure under critical annealing conditions is investigated. Theoretical calculations show that the stress on the porous GaN template is significantly reduced compared with the unannealed template. Using the metal organic chemical vapor deposition (MOCVD) method, a relaxed crack-free 60 μm thick GaN crystal film is grown on a porous GaN/sapphire substrate. The experimental results show that the stress of the GaN crystal grown on the high-temperature annealing porous template is greatly reduced, and the quality of the GaN crystal is significantly improved. Therefore, the high-temperature annealing porous template may be an excellent candidate for the growth of high-quality GaN crystals.