Multiple channel conduction analysis for material with multiple conductive paths

Magnetotransport and Hall measurements are very powerful techniques typically used to determine the density and mobility of carriers in a wide temperature range of materials. The analysis can be complicated when there are multiple conduction paths present. Traditionally mobility spectrum analysis is used to analyze such samples, where the mobility and carrier concentration is extracted via an iterative process that minimizes the error of model fit in each step. However, the method becomes computationally intensive even with two conducting channels. We devised a new method that puts additional constraints on the tunable parameters to reduce the computational load. Reducing the parameters to be electron and hole concentrations in a two channel analysis, we can then map the error of model fit in the electron-hole concentration parameter space. The desired model fit values are found in the global minimum of the error-parameter space. For analyzing magnetotransport data, we apply weighted least squares error for when the data is noisy to isolate true mobility values from background noise. We demonstrate application of the two channel analysis on two different bismuth-based material systems: bulk Bi0.88Sb0.12 and thin epitaxial films of (Bi1-xSbx)2Te3. The program we have developed revealed carrier concentration and mobility changes with temperature for the above materials. We will discuss optimum strategies for combining errors from longitudinal and transverse magneto-conductance. The analysis also gives an alternative approach to estimate the bandgap.