High-Sensitivity Picosecond-Response InxGa1-xAs Photodetectors

For ultrafast optoelectronic applications, photoconductors with sub-picosecond carrier lifetimes and low dark current are desired. Previous work has demonstrated the dramatic reduction in the carrier lifetime by lowering the growth temperature to ~200°C in molecular-beam-epitaxial (MBE) GaAs layers [1]. Optical transmission and reflection measurements, and photoconductive switching measurements have confirmed the sub-picosecond carrier lifetime in this material. In addition, the semi-insulating nature and high breakdown voltage of these layers has enabled the fabrication of submicron interdigitated photodetectors and optical correlators having an unprecedented bandwidth of 375 GHz and responsivity of ~ 0.1 A/W [2]. The excess-As incorporation during the low-temeprature MBE growth is believed to lead to the above properties [3], hence this approach of low-temperature growth should be applicable to other As-based materials. In particular, the ternary compound InxGa1-xAs is an important direct band-gap material for the long wavelength region, and with this in mind we investigate the ultrafast carrier dynamics and applications of low-temperature MBE grown InxGa1-xAs epilayers.