Mesoscopic Phenomena in Microstructures of IV–VI Epilayers

Abstract

Magnetoresistance measurements of photolithographically patterned PbSe and Pb1y Mnx Se microstructures were performed. Reproducible magnetoconductance fluctuations with the amplitude increasing with decreasing temperature were observed. Unexpectedly, these fluctuations contain a component periodic in the magnetic field, and their magnitude is greater than that expected from the current theory of the universal conductance fluctuations. Possible explanations are discussed.

Conductance fluctuations in PbTe wide parabolic quantum wells

“…The only requirement is the possibility for scattering of edge electrons to the 3D electron system at the contacts. In contrast, recently observed CF in other IV-VIepilayers, particularly PbSe and Pb 1-x Mn x Se single layers of thickness ranging from 1.5 -3 µm, exhibit a clearly non-universal amplitude which changes with the magnetic field [18,19]. However, there are no non-local data which would allow a more detailed comparison with our results.…”

Electron Transport in Submicron Wires of Semiconductors

“…Detailed studies showed homogeneous impurity distribution and good structural properties of the epilayers [8]. For IV-VI group we used PbTe:Bi films with thickness of 0.5 μm, grown onto BaF 2 substrate (with Ρb 0.94Eu0.06 Te buffer layer) and PbSe films with thickness of 1.7 μm, deposited directly onto BaF2 [9,10]. Electron concentration ranged from 1 x 10 16 to 6 x 1017 cm-3 .…”

“…The presence of edge channels were documented further by studies as a function of the line width and by a strong sensitivity of the conductance to the side-gate voltage as well as by large magnitude of both the UCF and the transverse magnetoresistance [6,10]. The strain effects present in IV-VI epilayers give a fascinating opportunity to construct high mobility quantum devices and study coherent transport.…”

“…Figure 4 shows local and nonlocal resistance of PbTe wire with Wgeo = 1 μm as a function of temperature. Note the extremely 1arge nonlocal component for T Ń 200 K. It was suggested that a difference between the thermal expansion coefficients of the substrate and the fllm below 200 K (which causes an overall biaxial tensile strain in the epilayer of the order of 1-2 x 10 -3 ) was responsible for the observed transport anomalies [10,6]. This difference leads to the biaxial strain, whose magnitude varies substantially near the wire edges (see inset).…”

Absence of nonlocal resistance in microstructures of PbTe quantum wells

“…Importantly, there was also another anomaly found in PbTe and PbSe epilayers, namely the occurrence of reproducible magnetoresistance fluctuations [31,32,61]. Their amplitude was anomalously high and could not be explained within the standard theory of universal conductance fluctuations [62,63].…”