The nitride semiconductor light emitting device has a light emitting region covering ultraviolet, blue, and green regions. In addition, such a GaN-based semiconductor light emitting device does not have a lattice matched substrate, and it is difficult...
The nitride semiconductor light emitting device has a light emitting region covering ultraviolet, blue, and green regions. In addition, such a GaN-based semiconductor light emitting device does not have a lattice matched substrate, and it is difficult to grow a high-quality nitride semiconductor thin film due to a large difference in lattice constant and thermal expansion coefficient. For this reason, a sapphire substrate is generally used to grow a GaN semiconductor thin film. In this study, I devised a method for controlling deformation of a substrate by deposition other materials on the back side of a GaN layer when the GaN based semiconductor layer is grown on the sapphire substrate. The deformation of the substrate caused by the process temperature, thickness and thermal expansion coefficient was calculated using finite element method. Based on these analysis results, the relationship between process temperature and material variables and displacement is derived. The range of the thermal expansion coefficient according to the process temperature and the thickness of the control layer for defining the displacement of the sapphire substrate within an allowable displacement range is estimated using the derived relational equation. The results of the derived relational equation were compared with those obtained by finite element analysis. Compared with the maximum displacement, the error result was 8.72%. Through this, it is possible to define the physical properties and thickness of the displacement control layer using the proposed relational expression without complex analysis and calculation in molding a semiconductor light emitting device using a 6-inch substrate.