Study of localized levels. II. The meaning of temperature-induced changes in activation on energies for electrical conduction

It is shown that the dominant-level approximation is a generally useful method for interpreting temperature-induced changes in Ohmic activation energy. Particular emphasis is placed on the situation where a change occurs due to a reversal of the inequality between the contributed and nonextrinsic carrier concentrations. All the prime causes for a temperatureinduced change in activation energy are considered and the temperature at which a change occurs is used to establish additional relationships between the dominant-state densities. A graphical means of computing the Fermi energy and locating localized-state densitites is also described. The analysis is applied to recent experimental results on gallium arsenide, silicon, and phthalocyanine and old results on germanium. The results show that impurity levels previously located via interpretation of activation energies for electric conduction are often incorrect and should be relocated, using the rules and procedures presented in this paper.