Low-temperature charge transfer in thallium-doped GaSe single crystals

S. Mustafaeva1, M. Asadov2 and A. Ismailov1

1Institute of Physics, National Academy of Sciences of Azerbaijan, Azerbaijan
2Institute of Chemical Problems, National Academy of Sciences of Azerbaijan, Azerbaijan

Keywords: single crystals, charge transfer,conduction mechanism
property: energy spread, jump distance,density of states near the Fermni level
material: GaSe

The aim of this work is to study the charge transfer in layered GaSe single crystals at low temperatures and to establish the conduction mechanism. The electric field was applied crosswise to the natural layers of GaSe single crystals. A silver paste was used as a contact material. The electrical measurements were performed in the temperature range 111–250 K on samples placed into a cryostat with a temperature stabilization system (the stabilization accuracy is 0.02 K). It is found that layer GaSe (1; 2 and 2.5 at. % of Tl) single crystals exhibit a variable range hopping conduction along the normal to their natural layers at temperatures T < 250 K in a dc electric field. Estimations are made for the density of states near the Fermni level (3.4 x 1017– 9.6 x1018 eV–1cm–3) and their energy spread (0.07–0.16 eV), the average jump distance (90–205 Å). We studied also the composition dependences of parameters of localized states in GaSe single crystals. It was shown that the introduction of thallium reduces the mean hop distance and activation energy of hoppings in GaSe. The electrical conduction and density of localized states near the Fermi-level increased with increasing composition of thallium in GaSe single crystals.

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