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 quant um wells. Identical M-plane (1 (1) over bar 00) and C-plane (0001) structur es 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 st rong polarization anisotropy of over 90% for the M-plane sample. The lumine scence is polarized normal to [0001] and shows no spectral shift with polar ization angle, i.e., it originates solely from A excitons (p(x) and p(y) va lence band states). The deviation of the polarization degree from unity is attributed to the mixing with p(z) valence band states due to quantum confi nement. (C) 2000 American Institute of Physics. [S0003-6951(00)01147-5].