ENERGY SELECTIVE OPTICALLY PUMPED STIMULATED-EMISSION FROM INGAN GAN MULTIPLE-QUANTUM WELLS/

Optically pumped stimulated emission (SE) from InGaN/GaN multiple quan tum wells (MQWs) grown by metalorganic chemical vapor deposition has b een systematically studied as a function of excitation photon energy ( E-exc) to further understand the origin of SE in these structures. Opt ically pumped SE was observed for excitation photon energies well belo w that of the absorption edge of the MQWs, indicating the states respo nsible for the soft absorption edge in these structures can efficientl y couple carriers with the gain region. ''Mobility edge''-type behavio r in the SE peak was observed as E-exc was varied. The effective mobil ity edge measured in these SE experiments lies similar to 110 meV abov e the main spontaneous emission peak and similar to 62 meV above the S E peak. Tuning the excitation energy below the mobility edge was found to be accompanied by a drastic increase in the SE threshold due to a decrease in the effective absorption cross section. The experimental r esults indicate that the SE peak observed here has the same microscopi c origin as the spontaneous emission peak, i.e., radiative recombinati on of localized states. (C) 1998 American Institute of Physics.