Magneto-optical investigation of the neutral donor bound exciton in GaN

We report on photoluminescence and magneto-optical experiments of the neutral donor bound exciton in GaN epitaxial films. At low temperatures we observe free and bound exciton recombination with a linewidth as narrow as 1.4 meV. For the magnetic field applied perpendicularly to the c-axis of the crystal the donor bound exciton line significantly broadens and, at a field of 12 T a partially resolved splitting into two lines is visible. For the magnetic field parallel to the c-axis, only a very small broadening occurs. We analyze this behaviour in analogy to CdS and present a first estimate of the heavy hole g-value in GaN.