Photoluminescence Decay Rate Research Articles

Carrier trapping in room-temperature, time-resolved photoluminescence of a GaAs/AlxGa1−xAs multiple quantum well structure grown by metalorganic chemical vapor deposition

The time decay of the room-temperature photoluminescence from the n=1 transition in a multiple quantum well structure grown by metalorganic chemical vapor deposition is observed to depend strongly on excitation energy density. For low excitation (0.2 μJ/cm2) an exponential 3-ns decay is observed, while for high excitation (120 μJ/cm2) the decay lengthens to 45 ns. In the case of higher excitation, the photoluminescence decay rate is observed to increase after excitation and initial decay. The excitation energy dependence of the initial decay can be explained by saturation of carrier traps, and the later speedup of photoluminescence decay can be explained by the release of carriers from the traps and subsequent refilling. Time-integrated photoluminescence data qualitatively support the trapping interpretation. This is the first report, to the best of our knowledge, of time-resolved photoluminescence in a metalorganic chemical vapor deposition grown GaAs/AlxGa1−x As quantum well structure.

Radiative recombination in inhomogeneous semiconductors.

Photoluminescence efficiencies and decay rates in inhomogeneous semiconductors depend of the ratio of thermal carrier energy to the energy of internal potential barriers caused by the inhomogeneities. At low temperatures, the barriers separate carrier pairs spatially and thus cause prolonged lifetimes and slowly decaying luminescence of reduced intensity. A criterion for inhomogeneity is found by time- and temperature-dependent luminescence experiments.

Photoluminescence decay times in (AlGa)As  GaAs multiple quantum well heterostructures

Measurements are reported of the photoluminescence decay rate from 55 Å GaAs(Al 0.35Ga 0.65)As multiple quantum well samples prepared by molecular beam epitaxy. Results are reported for the temperature range 4–295 K. Additional measurements of the external photoluminescence efficiency of single thin layers of (AlGa)As lead us to conclude that at the higher temperatures the lifetime in the quantum wells is limited by non-radiative recombination at or close to the (AlGa)As barriers. Following studies of the decay at 4 K we offer a possible alternative explanation of the free exciton decay mechanism to that postulated previously.