Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

First observation of fractional quantum Hall effect in a two-dimensional hole gas (2DHG) of selectively doped strained sGe/SiGe/(001)Si-based heterostructures

O.A. Mironov, E.L.Green, M.Uhlarz, M. Helm and D.R. Leadley

Nano Silicon Group,Department of Physics, University of Warwick, Coventry, UK

The extremely high 2DHG low temperature mobility of over 1.3*10⁶ cm²/Vs (Ps=2.9*10¹¹ cm^-2) [1-4] and very low hole effective mass (0.063 ± 0.001)Mo determined from unsplit Shubnikov-de Haas oscillations has enabled the fractional quantum Hall effect (FQHE) to be observed for the first time in the ranges of magnetic fields up to 16 T and temperatures 20 mK<T<4.2 K (HLD-IIBPMR,HZDR) . The SiGe/(001) Si-based heterostructures were grown by RP-CVD method (ASM, Epsilon 2000) [1-2] at University of Warwick. The 2DHG is located in a compressively strained (0.65%) sGe-QW of 20 nm thickness and 100% purity without any Si contamination from Si_0.2Ge_0.8 barriers. The sGe-QW was selectively doped by boron (single-sided doping with 26 nm spacer between QW and B-layer). The 2DHG low-temperature mobility in our system is more than one order of magnitude bigger than previously reported for similar SiGe-based heterostructures, in absence of parallel conduction to the 2DHG channel, and grown by use of LEPE-CVD [3] and MBE [5,6]. These results confirm that the FQHE is a truly universal and material independent phenomenon, which could be observed in strained or unstrained heterostructures with 2DEG or 2DHG.