Optimizing GaN/A1GaN Multiple Quantum Well Structures by TimeResolved Photoluminescence

We present the results of picosecond time-resolved photoluminescence (PL) measurements for GaN/A1Ga1N MQWs with varying structural parameters, grown by metalorganic chemical vapor deposition under the optimal (iaN-like growth conditions. We have shown that the optimal GaN/A1GaN (x 0.2) MQW structures for UV light emitter applications are those with well widths ranging from 12 and 42 A and barrier widths ranging from 40 to 80 A. The decreased quantum efficiency in GaN/AlGa1 N MQWs with well width L42 A is associated with an increased nonradiative recombination rate as L approaching the critical thickness of MQWs. For the barrier width dependence, whea the barrier width is below the critical thickness, the nonradiative recombination rate increases with a decrease of the barrier width due to the enhanced probabilities of the electron and hole wavefunctions at the interfaces as well as in the A1GaN barriers. On the other hand, the misfit dislocation density increases as the barrier width approaches the critical thickness, which can result in in enhanced noriradiative interface recombination rate. Our optimized GaN/AlGa1N MQW structures exhibited extremely high quantum efficiencies as well as a ratio ofwell emission intensity to barrier emission intensity exceeding iO.