The Kondo effect and mesoscopic quantum coherence in a 2D electron gas of magnetically undoped AlGaN/AlN/GaN heterostructures

Abstract

We report an observation of the Kondo effect in two-dimensional electron gas (2DEG) of magnetically undoped AlGaN/GaN high electron mobility transistor heterostructures and analyze the 2DEG magnetoresistance oscillations to reveal the small-scale structure of the confining potential. Temperature-dependent zero-field resistivity data exhibit an appreciable upturn below 120 K, followed by the standard low-temperature weak-localization (WL) behaviour below 50 K, crossing over to a pronounced weak antilocalization (WAL) picture at T < 3 K. Magnetotransport characterization was carried out in the temperature range 100 mK ÷ 300 K in the magnetic fields B up to 8 T, applied perpendicular to the 2DEG plane. The Altshuler-Aronov-Spivak oscillations of the magnetoresistance with period h/2e, clearly observed against the background of its smooth behavior, are determined by the inhomogeneity of the 2 DEG confinement and allows to estimate its characteristic spatial scales.