Time-Resolved Photoluminescence Determination of XZ -XX.Y Energy Separation and XZ State Lifetimes in AlGaAs/AlAs Type II Multiple Quantum Wells
Results of photoluminescence (PL) (steady-state and time-resolved with 150 ps resolution) experiments on a series of type II Al0.15Ga0.85As/AlAs multiple quantum wells with a (nominally) fixed alloy thickness of 4.0 nm and AlAs thicknesses ranging from 4.8 to 7.8 nm are reported. Samples with AlAs thickness less than 6.2 nm have the Xz state as the lowest lying conduction band level while for thicker AlAs layer the XX.Y states are lowest in energy. For samples with AlAs layers thicker than the critical value, a time-windowing technique is used to simultaneously observe PL from the Xz and lower-lying XX.Y states immediately following excitation by picosecond laser pulses. The energy separation of the two no-phonon lines directly yields the Xz- XX.y separation, and the decay rate from Xz to Xx.y can be obtained by time-resolving the hot Xz PL. The lifetime of the nonequilibrium Xz states in samples above the critical thickness is measured as a function of barrier thickness and uniaxial stress: it was found to depend weakly on the Xz- Xx.y separation from 3–9 meV, with values between 1 and 1.5 ns.
KeywordsUniaxial Stress Fast Component Picosecond Laser Pulse AlAs Layer Incident Fluences
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- 20.This data was taken on different pieces of wafers #5 and #6 from those used to obtain the spectra in Fig. 1.Google Scholar