The influence of strain-reducing layer on strain distribution and ground state energy levels of GaN/AlN quantum dot

This article deals with the strain distributions around GaN/AlN quantum dots by using the finite element method. Special attention is paid to the influence of Al_0.2Ga_0.8N strain-reducing layer on strain distribution and electronic structure. The numerical results show that the horizontal and the vertical strain components are reinforced in the GaN quantum dot due to the presence of the strain-reducing layer, but the hydrostatic strain in the quantum dot is not influenced. According to the deformation potential theory, we study the band edge modifications and the piezoelectric effects. The result demonstrates that with the increase of the strain reducing layer, the transition energy between the ground state electron and the heavy hole increases. This result is consistent with the emission wavelength blue shift phenomenon observed in the experiment and confirms that the wavelength shifts toward the short wavelength range is realizable by adjusting the structure-dependent parameters of GaN/AlN quantum dot.