%0 Journal Article %T Laser-Combined Scanning Tunneling Microscopy on the Carrier Dynamics in Low-Temperature-Grown GaAs/AlGaAs/GaAs %A Yasuhiko Terada %A Shoji Yoshida %A Osamu Takeuchi %A Hidemi Shigekawa %J Advances in Optical Technologies %D 2011 %I Hindawi Publishing Corporation %R 10.1155/2011/510186 %X We investigated carrier recombination dynamics in a low-temperature-grown GaAs (LT-GaAs)/AlGaAs/GaAs heterostructure by laser-combined scanning tunneling microscopy, shaken-pulse-pair-excited STM (SPPX-STM). With the AlGaAs interlayer as a barrier against the flow of photocarriers, recombination lifetimes in LT-GaAs of 4.0£¿ps and GaAs of 4.8£¿ns were successfully observed separately. We directly demonstrated the high temporal resolution of SPPX-STM by showing the recombination lifetime of carriers in LT-GaAs (4.0£¿ps) in the range of subpicosecond temporal resolution. In the carrier-lifetime-mapping measurement, a blurring of recombination lifetime up to 50£¿nm was observed at the LT-GaAs/AlGaAs boundary, which was discussed in consideration of the screening length of the electric field from the STM probe. The effect of the built-in potential on the signal, caused by the existence of LT-GaAs/AlGaAs/GaAs boundaries, was discussed in detail. 1. Introduction The development of semiconductor physics and devices has been progressing with the innovation of atomically controlled fabrication technologies [1¨C3]. However, the carrier dynamics in materials have been analyzed only by evaluating macroscopic functions, or with techniques that provide spatially and/or temporally averaged information. Microscopic carrier dynamics has not been directly observed, although it is fundamental for the device functions. Therefore, there has been an increasing desire for developing a microscopic technique that allows the investigation of carrier dynamics at high spatial and temporal resolutions. Laser-combined scanning tunneling microscopy (STM) is a promising candidate, because the tunneling junction itself responds on a time scale of a few femtoseconds and thereby ultrafast dynamics can principally be studied by STM with ultrashort pulse laser techniques [4¨C12]. Recently, we have reported a novel microscopy technique that enables the visualization of subpicosecond carrier dynamics in nanometer-scale structures [13], that is, shaken-pulse-pair-excited scanning tunneling microscopy (SPPX-STM) with a novel delay-time modulation method based on a pulse-picking technique [14¨C21]. A nonequilibrium carrier distribution is generated with ultrashort laser pulses and its relaxation processes are probed using STM by a pump-probe technique. We proposed a model clarifying the physical origin of the signal for semiconductors and verified it experimentally. The SPPX-STM signal consists of two components, that is, a faster one reflecting the decay process of bulk-side photocarriers and a %U http://www.hindawi.com/journals/aot/2011/510186/