THz Photoresponse and Magnetotransport of detectors made of HgCdTe/HgTe quantum well structures

In addition to space- and time-resolved measurements of the electrical generation of excited electrons in quantum Hall (QH) devices the dissipation in these devices induced by Terahertz (THz) laser impulses is investigated. For these tasks a THz laser system (p-Ge-Laser [1]) is applied. This laser uses transitions between Landau levels of light holes and emits laser impulses with an adjustable duration from 300 ns to some μs, tunably in the wavelength range 120μm < λ < 180μm. The THz laser radiation is used in order to stimulate charge carriers optically over the Landau-gap. The response of the sample to the laser impulses is in 2D-samples in the QH regime measured in order to receive data of the relaxation of the charge carriers. In this presentation we present photoconduction measurements of the HgTe/HgCdTe-(MCT) – quantum well devices in Hall bar, Corbino as well as combined Corbino- Hall bar geometry in the QH- regime. The materiel system HgTe/HgCdTe is characterized by a small effective mass (compared to GaAs [2], in our case 0.023m0) and accordingly smaller magnetic fields for the appropriate cyclotron energy.