Features of optical gain in heavily doped Al$_{x}$Ga$_{1-x}$N:Si-structures

Time-resolved luminescence and stimulated emission intensities has been experimentally investigated in heavily doped Al$_{0.65}$Ga$_{0.35}$N and Al$_{0.74}$Ga$_{0.26}$N structures under pulsed optical excitation. These results showed that the time decay of the luminescence and stimulated emission intensities for various wavelengths of the emitted spectrum and optical pumping intensities consisting of at least the fast and the slow components. Fast components with exponential time decay are responsible for the radiative recombination of nonequilibrium electrons on deep acceptors, while slow ones are responsible for the recombination of donor-acceptor pairs