Electrical Properties of Semiconductors

The accurate measure of semiconductor electrical properties is a fundamental step for the design and the correct operation of any electronic device. The electrical performance of any device will depend on how the carriers move inside the semiconductor lattice. The measure of the resistivity, the concentration of shallow and deep states, the charge carrier mobility, etc., allow for the design of new and advanced functionalities and for improvement in current device technology. In this chapter we will give a brief overview of the main electronic transport coefficients and experimental techniques used to investigate semiconductor materials and the main solar cell parameters. We have limited our attention to the most common and reliable techniques. Our work has been organised into seven sections. The first and second sections define the conductivity and the mobility of any material in terms of its band structure and looks at some semiconductor properties and the material doping. The third and fourth sections illustrate the main scattering mechanisms of charge carriers in a semiconductor and several experimental techniques to measure thin film resistivity, respectively. The fifth section introduces the Hall effect and defines the Hall coefficient and the Hall mobility, with a description of an experimental method to measure these. In the sixth section we report a brief analysis of deep state defects and we describe the DLTS technique to reveal them in a semiconductor lattice. Finally, in the seventh section we describe the current-voltage technique commonly used to measure the main solar cell parameters.

Keywords: Electrical Conductors, Resistance measurement, Conductivity tensor, charge carrier scattering, Hall mobility, Hall coefficient, van der Pauw geometry, Deep Level Transient Spectroscopy, Current-voltage, Solar cell electrical parameters.