Measuring the Effective Masses of the Electrical Conductivity and Density of States by Contactless Microwave Means

Resumo

Knowledge of the effective mass of quasiparticles is needed for studying the band structure of semiconductors, simulating processes of conductivity, and developing actual semiconductor devices. The problem of determining the effective mass of carriers in a particular sample is therefore of great interest. Using the example of silicon, it is shown in this work that it is possible to determine the effective masses of conductivity and the density of states by treating a measured microwave reflection spectrum as a set of information parameters. The inverse problem is solved of finding the conditions for the minimum of the difference of squares of values corresponding to known theoretical and experimentally measured spectral dependences. Calculations and experiments are performed for the temperature range of 130–190 K, in which the highest accuracy of measurements is ensured. For Ga-doped p-silicon and Sb-doped n-silicon, values of the desired effective masses are obtained that coincide with ones given in the literature. The proposed contactless technique allows simultaneous determination of the effective masses of conductivity and density of states of charge carriers using conventional equipment. The approach can be used to measure the parameters of other types of semiconductors, including ones that are little studied.