A Theoretical Calculation of Misfit Dislocation and Strain Relaxation in Step-graded InxGa 1-x N/GaN Layers

Abstract

This paper presents a theoretical calculation of misfit dislocation and strain relaxation in compositionally step graded InxGa1-xN grown on GaN using the total dislocation energy at each interface. The results also compared with uniform layer of In0.17Ga0.83N and In0.14Ga0.86N grown differently on GaN. Due to having residual strain and a step increase in indium composition a lower misfit strain in upper layers and hence larger critical thickness at each interface has been reported. These effects significantly reduced the misfit dislocations from 2.6×105cm-1to 9.5×104cm-1in step graded In0.14Ga0.86N(500nm)/In0.09Ga0.91N(100nm)/In0.05Ga0.95N(100nm)/GaN layers instead of a uniform In0.14Ga0.86N(700nm)/GaN. A small residual strain of 0.0007 after 700 nm graded layer thickness has been reported with 87.04% strain relaxation.