Density of states in Landau level tails of GaAsAlxGa1−xAs heterostructures

Abstract

From an analysis of the thermally activated resistivity as a function of the magnetic field in the quantum Hall regime we deduced the position of the Fermi energy in the mobility gap as a function of the filling factor and therefore the density of states. The measured density of states is best described by a Gaussian like profile superimposed on a constant background.

Activation transport under quantum Hall regime in HgTe-based heterostructure

“…As a rule, an assumption is used that the delocalized states with discrete energies Е = Е N are separated by the (mobility) gap Δ >> k B T, that leads to an expression [3][4][5]:…”

“…The DOS in mobility gaps may be evaluated from the data on activation energy E A as a function of the LL filling factor ν [3][4][5][6]. As / B n n ν = (n is the electron density, B n = / eB hc = is the degree of LL degeneracy), the filling factor can be tuned by the change of either a carrier density [3] or a magnetic field [4][5][6].…”

“…As / B n n ν = (n is the electron density, B n = / eB hc = is the degree of LL degeneracy), the filling factor can be tuned by the change of either a carrier density [3] or a magnetic field [4][5][6].…”

“…From the E A (B) dependences the background density of states in the mobility gap may be constructed [4,6,29]: Figure 5 shows the results for the DOS at mobility gaps ∆ 1 , ∆ 2 , and ∆ 3 (see also Table 1). The following features of the mobility gap DOS as a function of energy, D(E), should be mentioned.…”

“…Distances between adjacent LLs can be extracted and a density of localized states in the mobility gaps may be determined from scanning them by the Fermi level in experiments of this kind [3][4][5][6][7]. Experimental reconstruction of the energy spectrum is especially important for systems with a complex band structure where the LL picture is determined not only by the cyclotron energy with a given effective mass as for a simple parabolic conduction band system.…”