+ Terahertz emission from InGaAs with increased indium content

We have investigated the influence of indium content (x) increase on spectral characteristics of InxGa1-xAs photoconductor. To avoid the mismatch between crystalline parameters of In(x)Ga(1-x)A(s) and GaAs wafer we proposed to incorporate a step-graded metamorphic buffer layer. We showed that x increase strongly enhances THz emission and broadens THz spectrum of InxGa1-xAs. Since no polarity rehearsal of the THz waveform occurs and electron diffusion mobility increases up to 90% with x increase we attribute the increase of THz intensity to photo-Dember effect contribution. The maximum efficiency of optical-to-THz conversion was obtained for In-0.72.G(a0.28)As at optical fluence similar to 0.01 mu J/cm(2). The fabricated photoconductors can be used as promising photo-Dember or lateral photo-Dember THz emitters in pulsed THz spectroscopy and imaging, in particular, operating with long wave optical pump.