Depolarization effects in (1122)-oriented InGaN/GaN quantum well structures

Depolarization effects on electrical and optical properties of (1122)-oriented wurtzite (WU) InGaN/GaN quantum well (QW) were investigated using the multiband effective-mass theory. These results are compared with those of (0001)- and (1010)-oriented WU InGaN/GaN QW structures. The internal field is shown to become zero for (1122) crystal orientation near the crystal angle of 56°, 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 the (1122)-oriented QW 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)-oriented QW is found to have the optical gain comparable to that of the (1010)-oriented QW.