Anisotropic optical matrix elements in strained GaN quantum wells on semipolar and nonpolar substrates

In-plane optical anisotropies in compressively strained Ill-nitride quantum wells on semipolar and nonpolar substrates are numerically calculated using the 6 x 6 k center dot p Hamiltonian. It is shown that quantum confinement and compressive strain have the opposite effects on the anisotropies, and that the in-plane polarization degree is determined by the competition of these two effects. These characteristics are also verified by analytical calculation, and it is found that the signs of (A(4) - A(5)) and (D(4) - D(5)) are essential factors in determining the above-mentioned polarization properties, where A(4) and A(5) are valence band parameters and D(4) and D(5) are deformation potentials. On the basis of the calculation results, the structural design of laser diodes on semipolar and nonpolar substrates is also discussed.