Electronic and optical properties on non-polar InGaN/GaN quantum-well structures

Abstract

Electronic and optical properties of non-polar (112 macr0) a-(phi=0), (101macr0) m-plane (phi=pi/6), and (1122 macr)-oriented wurtzite (WZ) InGaN/GaN quantum well (QW) structures are investigated using the multiband effective-mass theory. These results are compared with those of (0001)-oriented WZ InGaN/GaN QW structures. The internal field becomes zero for (1122 macr) crystal orientation near the crystal angle of thetas=56deg, in addition to a-and m-plane with thetas=90deg irrespective of the In composition in the well. This is because the sum of the piezoelectric and spontaneous polarizations in the barrier is equal to that in the well. The optical gain of QW structures with non-polar crystal orientation is significantly larger than that of the (0001)-oriented QW. This is caused mainly by the increase of the optical matrix element due to the disappearance of the internal field. Also, the (1122 macr)-oriented QW is found to have the optical gain comparable to the a-or m-plane QW. In addition, their optical matrix element show strong in-plane anisotropy. The bandgap transition wavelength of the QW structure with the m-plane is found to be longer than that of the QW structures with the a-plane.