The mechanism of generation of the donor- and acceptor-type defects in the n-TiNiSn semiconductor heavily doped with Co impurity

Temperature dependences of resistivity, thermoelectric coefficient, and structural characteristics of the n-TiNiSn intermetallic semiconductor heavily doped with Co impurity (the Co concentration NCo ∼ 9.5 x 1019-1.9 x 1021 cm-3) have been studied in the temperature range 80-380 K; the distribution of the electron density of states is also calculated. It is shown that, in TiNi1-xCoxSn with x < 0.03, the impurity atoms occupy crystallographic sites of atoms Ti and Ni simultaneously and in various proportions and generate the donor and acceptor defects, respectively. It is established that there is a relation between the impurity concentration, the amplitude of a large-scale fluctuation, and also the degree of filling of the potential well of a small-scale fluctuation (fine structure). The results are discussed in the context of the Shklovskii-Efros model of a heavily doped and compensated semiconductor.