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

In addition to spaceand 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 <  < 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 2Dsamples 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 CorbinoHall bar geometry in the QHregime. 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.