Optical anisotropy in nonpolar (1120)-oriented a-plane InGaN/GaN quantum wells

Optical anisotropy in nonpolar ((1) over bar(1) over bar 20)-oriented a-plane InGaN/GaN QWs was investigated using the multiband effective-mass theory. In the case of the Gamma point (k(parallel to) = 0), the optical matrix elements for y'-polarization are much larger than those for x'-polarization because the states constituting the topmost valence subband at the Gamma point are predominantly vertical bar Y' >-like in the ((1) over bar(1) over bar 20)-oriented QW. On the other hand, the optical anisotropy rapidly decreases with increasing in-plane wave vector and becomes zero at higher k(parallel to). This may be attributed to the fact that the state of the first subband is equally mixed vertical bar X > and vertical bar Y > at large k(parallel to). The in-plane optical anisotropy is shown to be nearly independent of the In composition.