High power and high bandwidth photoconductive terahertz emitters and detectors made of iron doped InGaAs

Summary form only given. In non-destructive testing (NDT) and industrial process monitoring [1], reflection geometry is commonly preferred over transmission, because only one-side access to the sample is possible. State-of-the-art terahertz (THz) time domain spectroscopy (TDS) systems hitherto use different emitter and detector devices [2], such that either an angled THz beam path or a beam splitter is required to enable reflection measurements. This leads to rather bulky and complex setups. An integrated THz device, combining the emitter and detector on a single chip, would significantly facilitate reflection measurements. For competitive integrated devices a photoconductive material, which is both compatible to the excitation with 1550 nm femtosecond pulses and applicable as THz emitter and detector has to be found.In this paper we show that iron (Fe) doped InGaAs grown at temperatures around 400 °C by gas-source molecular beam epitaxy (MBE) combines all these properties. Due to the relatively low growth temperature during MBE Fe doping concentrations up to 5 ×1020 cm-3 can be obtained. In addition, the material features an electron lifetime of 300 fs, a resistivity above 2 k cm and an electron mobility higher than 900 cm2V-1s-1. Thus, InGaAs:Fe combines the sub-picosecond lifetime required for broadband photoconductive receivers with the high resistivity and the high mobility needed for efficient THz emitters.