Electrical Properties of Germanium Selenide GeSe

Experimental studies were made of electrical resistivity and Hall coefficient of stoichiometric, non-stoichiometric and impurity-doped GeSe crystals over the temperature range from 100°K to 800°K. The energy gap was estimated to be nearly 1.0 eV from the slope of the resistivity curves at high temperatures. There were two ways in which hole mobility varied with temperature: one was as T -2.0 and the other as T 4.3 . The results on low temperature Hall coefficient were qualitatively interpreted on the assumption that there were two kinds of impurity levels in GeSe, one of which was acceptor level due to the impurity atoms common to all specimens and the other donor level or trapping center of holes due to germanium atoms in excess of stoichiometry. An anomalous behavior found in the Hall coefficient was explained by the same assumption as in the case of SnSe that new acceptors were introduced into GeSe by heat-treatment at high temperatures and that these introduced acceptors were annihilated by the heat-treatment at lower temperatures.