Carrier dynamics in low-temperature-grown AlxGa1-xAs/GaAs multiple quantum wells
Abstract
Femtosecond pump-probe spectroscopy has been used to study ultrafast relaxation dynamics in low-temperature-grown AlGaAs/GaAs multiple quantum wells (MQW’s). It was found that the carrier lifetime of as-grown MQW’s was much longer than those that had been subjected to 30 s rapid thermal annealing. The carrier lifetimes of samples annealed to three different temperatures (600, 700, and 800 °C) were measured and that annealed to 700 °C was found to be shorter than that of the other two. We also observed the quantum beats of heavy-hole and light-hole exciton in as-grown AlGaAs/GaAs MQW’s at low temperature, but not in the annealed samples. The beat frequency was 3.7 THz, corresponding to the energy difference between heavy- and light-hole excitons in the as-grown AlGaAs/GaAs MQW’s. As the temperature rose, the beats disappeared. We gave two possible reasons to explain this phenomenon. We tuned the central frequency of femtosecond Ti:sapphire laser through the resonant frequencies of heavy holes and light holes, while the phase of the quantum beats did not change.
- Publication:
-
Physical Review B
- Pub Date:
- April 2003
- DOI:
- 10.1103/PhysRevB.67.134304
- Bibcode:
- 2003PhRvB..67m4304L
- Keywords:
-
- 78.47.+p;
- 78.66.Fd;
- 78.40.Fy;
- Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter;
- III-V semiconductors;
- Semiconductors