Weighted Mobility

Engineering semiconductor devices requires an understanding of charge carrier mobility. Typically, mobilities are estimated using Hall effect and electrical resistivity meausrements, which are are routinely performed at room temperature and below, in materials with mobilities greater than 1 cm2 V‐1 s‐1. With the availability of combined Seebeck coefficient and electrical resistivity measurement systems, it is now easy to measure the weighted mobility (electron mobility weighted by the density of electronic states). A simple method to calculate the weighted mobility from Seebeck coefficient and electrical resistivity measurements is introduced, which gives good results at room temperature and above, and for mobilities as low as 10−3 cm2 V‐1 s‐1, μw=331cm2Vs(mΩ cmρ) (T300 K)−3/2[ exp[ |S|kB/e−2]1+exp[−5(|S|kB/e−1) ]+3π2|S|kB/e1+exp[5(|S|kB/e−1) ] ]Here, μw is the weighted mobility, ρ is the electrical resistivity measured in mΩ cm, T is the absolute temperature in K, S is the Seebeck coefficient, and kB/e = 86.3 µV K–1. Weighted mobility analysis can elucidate the electronic structure and scattering mechanisms in materials and is particularly helpful in understanding and optimizing thermoelectric systems. The weighted mobility, easily computed from measurements of the Seebeck coefficient and electrical resistivity, is an accurate measure of the charge carrier mobility and effective mass. It is even more sensitive than measurements of the Hall effect for revealing electron transport mechanisms in complex materials ranging from metals, semiconductors, and conducting polymers.