Terahertz photoresponse of AlInSb/InSb/AlInSb quantum well structures

Abstract

We have studied the photoresponse ͑transmission and photoconductivity of Corbino-shaped devices͒ of structures with InSb quantum wells ͑AlInSb barriers͒. To characterize the devices, the Shubnikov-de Haas ͑SdH͒ effect up to magnetic fields B of 7 T and current-voltage ͑I-V͒ characteristics at various magnetic fields were measured. Some of the samples showed clearly resolvable SdH oscillations. The I-V curves showed pronounced nonlinearities. The phototransmission and the photoconductivity at various terahertz ͑THz͒ frequencies were measured around 2.5 THz generated by a p-Ge laser. From the cyclotron resonance ͑transmis-sion measurements͒ we deduced a cyclotron mass of 0.022m 0 . We also performed photoconductivity measurements on Corbino-shaped devices in the THz frequency range. Oscillations of the photoconductivity with maxima near the minima of the conductivity in the dark were observed. Thus, these devices are potentially suitable for the detection of THz radiation.

Interplay of spin and orbital magnetogyrotropic photogalvanic effects in InSb/(Al,In)Sb quantum well structures

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] The characteristics driving the interest in this novel narrow gap material are the high carrier mobility, small effective masses, large Landé g * factor, possibility of the mesoscopic spindependent ballistic transport, and a strong spin-orbit coupling. The latter gives rise to a number of optoelectronic effects such as, e.g., terahertz photoconductivity 15 and the circular photogalvanic effect [16][17][18][19][20][21][22] recently observed in InSb QWs. 23 Investigation of photogalvanic effects in the presence of a magnetic field should provide further access to nonequilibrium processes in low-dimensional structures, yielding information of such details as the anisotropy of the band spin splitting, processes of momentum and energy relaxation, symmetry properties, and the Zeeman spin splitting (for review, see Refs.…”

The detection of terahertz waves by semimetallic and by semiconducting materials

“…From the nonlinearities in the I-V curves, the operational conditions of the samples working as terahertz detectors can be determined. 12 At voltages closely below the critical value V C of the breakdown of the QH effect ͑QHE͒, an additional optical excitation of the sample can result in completing the breakdown of the QHE. 12 The breakdown of the QHE leads to a measurable increase in the radial conductivity xx of a Corbino device.…”

“…12 At voltages closely below the critical value V C of the breakdown of the QH effect ͑QHE͒, an additional optical excitation of the sample can result in completing the breakdown of the QHE. 12 The breakdown of the QHE leads to a measurable increase in the radial conductivity xx of a Corbino device. Thus, the PC can be registered by measuring the increase in the source-drain current I SD at samples prebiased by subcritical ͑but high enough͒ source-drain voltages V SD Ͻ V C .…”

“…12,14 In the case of InSb samples, we can deduce the energy difference between the subband energy E s and the Fermi energy E F , ⌬E = E s − E F . 12 For the samples with HgTe QWs, ⌬E cannot be generally determined from the corresponding m c values. This is because of the rather complicated band structure E͑k͒ for these samples.…”

“…The latter property is necessary for instance for the identification of substances by terahertz radiation and does not occur in bolometer detectors. The characteristic data n s and e are deduced from magnetotransport measurements at low temperatures ͑1.5 K Յ T Յ 4.2 K͒ and in the range of the magnetic field 0 Յ B Յ 10 T. The PR investigations presented here are performed using our p-Ge laser emitting terahertz waves in the wavelength range 120 m ՅՅ180 m. 8,9,12 Our laser is continuously tunable in the aforementioned wavelength range by changing the magnetic field B laser ͑generated by a superconducting coil͒ at the Ge crystal in the range 2.75 T Յ B laser Յ 4.13 T.…”