Density of states of the two-dimensional electron system at Si-MOS and Si-MNOS devices in the quantum Hall regime

• Published in: Surface science 1991-07, Vol.250 (1), p.243-250
• Main Authors: Nachtwei, G., Salchow, O., Breitlow, C., Jaeger, A., Krüger, H.
• Format: Article
• Language: English
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(91)90727-A

The measurement of activation energies for various positions of the Fermi level between two Landau levels provides an opportunity to evaluate the density of states (DOS) in the quantum Hall regime. We present results of measurements of the temperature dependence of the magnetoresistivity ϱ xx at filling factors ν = 2 and ν = 4 for several Si-MOS and MNOS samples with the same layout but different insulator layers of SiO 2 or SiO 2/Si 3N 4, respectively. The Hall mobility of the MNOS structures is noticeably higher than that of the MOS structures, whereas the DOS determined from activation energy measurements is lower. The measured DOS is higher than the simple overlap of two adjacent Gaussian-shaped Landau bands with broadening parameters taken from the Hall mobility data. This can be explained by a constant background contribution to the DOS. For the i = 2 plateau an estimate of the effective Landé-factor can be given.