HgTe-CdTe superlattices: Experimental and theoretical curves of band gap versus HgTe layer thickness

An experimental curve of room-temperature band gap versus HgTe layer thickness for HgTe-CdTe superlattices is presented for the first time. The room-temperature experimental results are compared to theoretical results determined using the envelope function approximation. Also a few values of the band gap at 2 K are given and compared to theoretical predictions. A good agreement between experiment and theory is found

MAGNETO-OPTICAL STUDY OF A HgMnTe-CdTe SUPERLATTICE

Des transitions interbandes et de resonance cyclotron sont observées dans des expériences de magnéto-absorption réalisées dans un super-réseau HgMnTe-CdTe entre 1,5 et 10K. L'effet de l'aimentation des ions Mn est mis en évidence en fonction de la température.Cyclotron resonance and interband transitions are observed in far infrared and infrared magneto-absorption experiments on a HgMnTe-CdTe superlattice for temperatures from 1.5K to 10K. The cyclotron resonance transitions display temparture-dependent energy shifts which are consistent with the effects of changing magnetization of the dilute Mn impurities

Graphene nanotransistors for RF charge detection

We have studied the static and dynamical properties of a graphene microwave nanotransistor to be used as sensitive fast charge detectors. The channel consists of exfoliated graphene on SiO2 with a 120 nm long, 900-1500 nm wide top-gate deposited on 5 nm AlOx dielectric. The scattering parameters were measured up to 60 GHz from which we deduce the gate capacitance, the drain conductance and the transconductance as a function of gate voltage. The broad measuring band allows us to measure the current gain and to map its full spectrum so as to extract reliable values of the transit frequency fT. From these measurements, we could estimate the carrier mobility, the doping of the access leads, the gate capacitance and the transconductance. The transconductance per unit width and bias voltage is larger than 1mSμm−1 V−1 which compares with the performance of high electron mobility transistors. High-frequency characterization is achieved using microwave probe stations. Finally, using recent noise thermometry measurements, we estimate the charge resolution of graphene nanotransistors