Origin of tensile strain in GaN grown on AlGaN/AlN stress mitigating layers on 100-mm Si (1 1 1) by ammonia molecular beam epitaxy

The origin of tensile strain in GaN grown on AlGaN/AlN stress mitigating layers on 100-mm Si (1 1 1) was investigated by varying the AlGaN growth temperature. GaN grown on higher AlGaN growth temperature exhibited two dimensional growth mode while three dimensional growth mode was obtained for GaN grown on lower AlGaN growth temperature. Micro-Raman and high-resolution X-ray diffraction techniques were employed to measure the residual tensile strain in GaN. The average plastic relaxation was calculated to obtain the tensile strain in GaN due to dislocation looping. The measured and calculated residual tensile strain values were compared to determine the origin of tensile strain. The average plastic relaxation and the tensile strain generated due to the grain coalescence were found to be the major factors influencing the strain states of GaN grown on AlGaN/AlN stress mitigating layers, in addition to the tensile strain generated due to the thermal mismatch.

► Origin of tensile strain in GaN grown on AlGaN/AlN stress mitigating layers.
► GaN shows 3D and 2D growth mode on AlGaN grown at different growth temperatures.
► Dislocation looping causes plastic relaxation of GaN grown in 2D growth mode.
► Grain coalescence generates additional tensile strain in 3D grown GaN.
► Si diffusion may not be the source of tensile strain in GaN.