Terahertz photoconductivity in GaAs/AlGaAs and HgTe/HgCdTe quantum Hall devices

Abstract

We present measurements of the THz photoconductivity on different quantum Hall systems. GaAs/AlGaAs and HgTe/HgCdTe (MCT) heterostructures with Hall-bar and Corbino geometry are investigated. A recipe for the preparation of metallic Corbino contacts on MCT is shown. The system is excited by the radiation of a p-Ge laser (tunable from 1.7 to 2.5 THz) and the photoresponse (PR) is measured versus the magnetic field B. We observe enhanced PR around integer filling factors (bolometric PR) and cyclotron resonance (CR) effects. Because of the lower effective mass in MCT, the CR in this system appears at a relatively low magnetic field (≈ 2 T). This is appropriate for possible applications. Finally we present time resolved measurements of the PR on the GaAs system. We find relaxation times from about 10 to over 200 ns, which depend on the geometry, the applied source-drain voltage and the on mobility of the sample.

Growth of HgTe Quantum Wells for IR to THz Detectors

“…13 Terahertz conductivity in the Hall bar was observed in HgTe QWs under laser excitation with Ge active medium between 1.7 THz and 2.5 THz (corresponding to wavelengths of 120 lm to 180 lm). 14 Single-wave ellipsometry was very effective for controlling MBE growth of HgCdTe alloys with designed composition profiles throughout the thickness for different IR detector applications. 15 Theoretical ellipsometric parameter trajectories were calculated for an MBE-grown HgTe/CdTe SL 16 and confirmed experimentally for HgCdTe potential barriers, wells, and periodical structures 100 nm in thickness.…”

Detection of terahertz and sub-terahertz wave radiation based on hot-carrier effect in narrow-gap Hg1−xCdxTe

“…One can see from Fig. 4 that for the carriers concentration p~7×10 16 cm -3 , the photoresponse was 3 times more than for the con− centration n~1.2×10 14 cm -3 at 77 K. Moreover, the maxi− Detection of terahertz and sub−terahertz wave radiation based on hot−carrier effect in narrow−gap Hg 1-x mum of output signal for p−type samples could be shifted to the high temperature region (130-190 K depen− ding on the carrier's concentration) that is benefit compa− ring to other known detectors of THz radiation. Another benefit is the sensitivity of the proposed detector in the broadband.…”

“…As the material for creation of THz−detectors, Hg 1-x Cd x Te was used in receivers on superlattices and heterojunctions HgTe/CdHgTe [15,16]. The possibility of detector creation that is sensitive in the far infrared region and that is based on the effect of electrons heating in semiconductors was pre− dicted by Rollin in 1961 [17].…”

Optically and electrically induced dissipation in quantum Hall systems

“…Hall bars and Corbino-shaped devices patterned from GaAs/GaAlAs heterojunction wafers [3][4][5][6][7][8][9][10][11][12][13][14][15][16]38] and from HgTe/HgCdTe quantum well wafers [14][15][16][17][18] were exposed to THz waves.…”