In-plane polarization anisotropy of the spontaneous emission of M-plane GaN/(Al,Ga)N quantum wells

We study the in-plane polarization of wurtzite GaN/(Al, Ga)N multiple quantum wells. Identical M-plane (1 (1) over bar 00) and C-plane (0001) structures are grown by plasma-assisted molecular-beam epitaxy on gamma -LiAlO2(100) and 6H-SiC(0001), respectively. While the emission from the conventional [0001] oriented wells is isotropic within the growth plane, we observe a strong polarization anisotropy of over 90% for the M-plane sample. The luminescence is polarized normal to [0001] and shows no spectral shift with polarization angle, i.e., it originates solely from A excitons (p(x) and p(y) valence band states). The deviation of the polarization degree from unity is attributed to the mixing with p(z) valence band states due to quantum confinement. (C) 2000 American Institute of Physics. [S0003-6951(00)01147-5].