Ultrafast carrier dynamics in LT-GaAs doped with Si delta layers

摘要

We characterized the ultrafast properties of LT-GaAs doped with silicon delta-layers and introduced delta-doping (delta-doping) as efficient method for enhancing the properties of GaAs-based structures which can be useful for terahertz (THz) antenna, ultrafast switches and other high frequency applications. Low temperature grown GaAs (LT-GaAs) became one of the most promising materials for ultrafast optical and THz devices due to its short carrier lifetime and high carrier mobility. Low temperature growth leads to a large number of point defects and an excess of arsenic. Annealing of LT-GaAs creates high resistivity through the formation of As-clusters, which appear due to the excess of arsenic. High resistivity is very important for THz antennas so that voltage can be applied without the risk of breakdown. With delta-Si doping, control of As-clusters is possible, since after annealing, clusters align in the plane where the delta-doping occurs. In this paper, we compare the properties of LT-GaAs-based planar structures with and without delta-Si doping and subsequent annealing. We used pump-probe transient reflectivity as a probe for ultrafast carrier dynamics in LT-GaAs. The results of the experiment were interpreted using the Ortiz model and show that the delta-Si doping increases deep donor and acceptor concentrations and decreases the photoinduced carrier lifetime as compared with LT-GaAs with same growth and annealing temperatures, but without doping.