Investigations of sodium in bridgman-grown CuInSe2

Measurements of thermoelectric power (¿) and electrical resistivity (¿) were made at room temperature on filamentary samples of CuInSe
²
(stoichiometric) and CuInSe
_2.2
(excess Se), Bridgman-grown with added elemental sodium in the melt in the amounts of 0, 0.1, 0.2, 0.5, 1, 2 and 3 at. %. In the CuInSe
₂
+ Na samples, conversion from p- to n-type occurred between 0.2 and 0.5 at. % Na, yielding electron concentrations of the order of 10
¹⁶
cm
^-3
. By contrast, the CuInSe
_2.2
+ Na samples remained p-type at all the sodium addition levels, yielding hole concentrations of the order of 10
¹⁸
cm
^-3
. In the important range 0 to 0.5 at. % Na, where sample brittleness is less of a problem than for higher additions, no major changes occurred in hole mobility or resistivity but a small increase in ¿
_p
and a small decrease in ¿ was apparent at 0.1 at. % Na.