Highly sensitive and tunable detection of far-infrared radiation by quantum Hall devices

Abstract

We studied far-infrared ͑FIR͒ response due to cyclotron resonance ͑CR͒ of two-dimensional electron gas systems in GaAs/AlGaAs heterostructures by using cyclotron radiation from n-InSb devices as the illumination source. We examined the dependence of the FIR response on different experimental parameters, including the aspect ratio of Hall bars, electron mobility, bias current, illumination intensity, magnetic field, and lattice temperature. A strong photoresponse emerges only in the vicinity of integer quantum Hall effect ͑IQHE͒ regimes. Time-resolved measurements show that the recombination lifetime of excited carriers depends largely on the electron mobility, ranging from 5 s to 1 ms at 4.2 K. The temporal decay of photoresponse is nonexponential in higher-mobility samples, whereas it is exponential with a single time constant in lower-mobility samples. This, together with the relatively large time constants, suggests that the FIR response is induced through multitrapping processes, in which excited carriers in Landau levels are repeatedly captured by localized states and reexcited to delocalized states. This multitrapping process is suggested to be promoted by the CR-induced heating of the electron system. Theoretical calculation based on the electron heating model reasonably reproduces characteristic dependence of the photoresponse on the magnetic field in the vicinity of IQHE plateaus. The IQHE Hall bars serve as a high-sensitive narrow-band FIR detector, where the highest sensitivity reaches ϳ10 8 V/W. Tunability of the detector is demonstrated by varying the electron density. We discuss briefly the design of high-sensitive FIR detectors using the IQHE Hall bars.

Light-induced electron localization in a quantum Hall system

“…The observed relaxation time of the localized state in Fig. 2a (a few microseconds) is comparable to the previously reported value on a similar trapped state 20 , which supports the above localization mechanism.…”

“…kind [15][16][17][18][19][20][21] was done in an ideal quantum Hall state and explained by the heating effect due to the nanosecond to microsecond terahertz pulses they employed. Therefore, the idea of light-induced IQHE has not been explored yet.…”

Time constant of the far-IR response of a quantum Hall device

“…7 As with two-dimensional electron gas (2DEG) (/4.2K = 8 x 10 5 cm 2 "s, n, = 2.8 x 1011 cm-2 ). They have a long 2DEG channel 50 #tm x 170rmm in size patterned in a zigzag shape and fitted into an area of 4 x 4 mm 2 [1,5]. The sample placed in the liquid helium in the center of a superconducting solenoid was biased by a d.c. current of 3 LtA.…”

“…The finite Rxx emerges when electrons and holes are excited by FIR radiation at cyclotron resonance (CR) in the delocalized (extended) states near the Landau level centers above and below the Fermi level EF. A thorough investigation of the photoresponse has been undertaken recently [5]. The results obtained revealed the key role of the random potential in the mechanism of FIR-photoresponse.…”

“…Quantum Hall effect (QHE) device is known to be a sensitive detector of far infrared (FIR) radiation [1][2][3][4][5]. At QHE the Hall resistance is quantized and the longitudinal resistance Rxx vanishes.…”