Microwave mixing and noise in the two-dimensional electron gas medium at low temperatures

Abstract

Microwave mixing and noise measurement techniques have been used to characterize energy relaxation and noise phenomena for the two-dimensional electron gas (2DEG) medium in single AlGaAs/GaAs modulation-doped quantum wells. Mixing experiments at 94 GHz yield the energy relaxation time directly, in good agreement with optical methods previously reported. The noise output power at low microwave frequencies (1.5–3.5 GHz), is shown to have one term due to Nyquist noise at the electron temperature, and a second frequency-dependent term caused by fluctuations in the electron temperature.

Ultrafast two-dimensional electron gas detector and mixer for terahertz radiation

“…D can be estimated by using the measured temperature dependence of the mobility. 6 Under optimum mixing conditions, the electric field was 150 V/cm, the bias current 3 mA, and the mobility 60 000 cm 2 /V s. 6,7 Assuming that the Einstein relation is at least approximately valid, we find D ϭ500 cm 2 /s. This value is close to values measured in similar 2DEG samples.…”

“…Another semiconductor medium, the two-dimensional electron gas ͑2DEG͒ at an AlGaAs/GaAs interface, was later shown to be capable of bandwidths up to 3 GHz. 6,7 The 2DEG HEB mixer was demonstrated by performing measurements at 94 GHz, but has not subsequently been implemented for THz use. Partly, this is due to the very successful development of THz HEBs consisting of thin-film superconductors ͓Nb ͑Ref.…”

“…We will assume n s ϭ3ϫ10 11 cm Ϫ2 . The dimensions of the device used by Yang et al 7 were Lϭ5 m by Wϭ50 m. For this device the IF bandwidth was measured to be 3 GHz, while the devices used by Yang et al 6 yielded B G ϭ1.8 GHz. We will assume the former value, which translates to a thermal time constant ͑energy relaxation time͒ ϭ50 ps.…”

“…The device would be a shorter version of the device which has already been demonstrated. 5,7 For use at THz frequencies it could be coupled quasioptically to an antenna/ dielectric lens combination, as used in a number of low-noise THz superconducting HEB mixers. 1-4 A typical antenna on silicon has an impedance of about 80 ⍀ so the device width would be adjusted to give this resistance.…”

Millimeter/submillimeter mixing based on the nonlinear plasmon response of two-dimensional electron systems

“…However, owing to the inertness of the cooling of hot charge car riers through the interaction with phonons or diffusion cooling, the device transmission band is no wider than 10 GHz. Mixers on a two dimensional electron gas in AlGaAs/GaAs semiconductor heterostructures [5,6] constitute an alternative type of bolometric hetero dyne detectors operating at temperatures of up to 80 K. The maximum attainable transmission band for the case of the cooling of hot charge carriers on the optical phonons of the lattice is 4 GHz [5][6][7]. The transmission bands for the cases of the cooling of hot charge carriers owing to their diffusion and ballistic emission to the contacts are 20 [8] and 40 GHz [9], respectively.…”