Anisotropic Optical Matrix Elements in Strained GaN Quantum Wells on Semipolar and Nonpolar Substrates

In-plane optical anisotropies in compressively strained III–nitride quantum wells on semipolar and nonpolar substrates are numerically calculated using the 6×6 k· 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.