Strain relaxation and improvement of epi-layer quality using step-graded layers for MOVPE InxGa1−xN (x ∼ 0.4)

This paper presents the evidence of strain relaxation and improved quality of MOVPE In_xGa_1-xN using step graded interlayers. A compositionally step-graded In_xGa_1-xN is grown on GaN template by controlling temperature from 750° to 900° C with optimum TMI/(TMI+TEG) molar ratio. Using two interlayers the lattice mismatch of 0.33, 0.31 and 0.59 between the successive layers are measured from reciprocal space map (RSM) which improves the film quality. The measured value of tilt and twist with the indium composition of 0.17, 0.29 and 0.39 reveals that more interlayer is necessary to reduce the dislocation density for higher indium content sample. We also attributed the improvements of crystalline quality using step-graded layer from the PL data.