# 4

CuGaSe2, briefly CGS, belongs to the I-III-VI2 group of chalcopyrite compounds. CGS attracted attention as a very promising material for photovoltaic applications. Efficiencies exceeding 9 % have been obtained for single crystals as well as thin film solar cells [1]. Recently it has been demonstrated that n-type CGS can be achieved by codoping with Ge and Zn [2]. The preparation of n-CuGaSe2 is expected to be helpful for improvement of the efficiency of photovoltaic devices. Investigations of the Hall effect, the conductivity σ and the mobility of n-CGS single crystals between T = 2–300 K yielded the values of the gap between the conduction band and the impurity band, the concentration of donors and acceptors, and allowed to determine scattering mechanisms at T>100 [3]. In this paper investigations of the low-temperature (T = 100 to 2 K) conductivity in zero and non-zero (B up to 8 T) magnetic field are presented to study mechanisms of hopping charge transfer and parameters of the localized electrons of n-CGS. CuGaSe2 single crystals were grown by chemical vapor transport using iodine as a transport agent. Ge ion implantation was performed on Cu-annealed single crystals. To achieve n-type conduction the samples were annealed in the presence of Zn. Samples # L1 and L2 were annealed for 10 min by rapid thermal annealing, whereas samples # 3 and # 4 were slowly ramped to the annealing temperature and held at the elevated temperature for 1 h