Elementary technique to measure the energy band gap and diffusion potential of p n junctions

This paper describes three simple experimental exercises suitable for one or more laboratory periods in which the students measure the forward current voltage, the forward rate of change of junction voltage with temperature, and the reverse capacitance voltage characteristics of a pn junction. Using these data the students determine the energy band gap of the semiconductor, the diffusion potential, the ideality factor, and the degree of abruptness of the junction. For these experiments we use junctions fabricated with Ge, Si, GaAs0.6P0.4, and GaP semiconductors. For each of these semiconductors the measured energy band gap is found to be within 5% of the accepted values and the measured junction parameters are consistent with expected values.