OPTICAL GAIN IN GAINN GAN HETEROSTRUCTURES

By optical gain spectroscopy we have studied the fundamental laser pro perties of GaInN/GaN heterostructures grown on sapphire. Utilizing the stripe excitation method we have measured optical gain spectra at roo m temperature. Due to the low symmetry of the wurtzite structure and t he resulting splitting of the uppermost valence bands, we find optical gain only for the TE mode. Our analysis shows that the optical gain i s due to direct band-to-band transitions in an electron-hole plasma. F or gain amplitudes typically found in lasers, we find carrier densitie s up to 3 x 10(19) cm(-3), which are likely to lead to rather large th reshold current densities. (C) 1996 American Institute of Physics.