AMBIPOLAR DIFFUSION AND AMBIPOLAR CARRIER DRIFT IN CUINSE2 FILMS

The ambipolar diffusion of charge carriers at room temperature has bee n studied in p-type CuInSe2 films 1-3 mu m thick. The CuInSe2 films we re grown through simultaneous vacuum deposition of the constituents of the compound. The method of an interference grating of photocarriers was used for the measurements. The ambipolar diffusion length L was ca lculated from the dependence of the secondary photocurrent measured in the direction perpendicular to the interference fringes of the gratin g on the lattice constant. The results show that L is comparable in ma gnitude to the dimensions of the crystals in the film (from 360 to 420 nm). The diffusion length is analyzed as a function of the illuminati on intensity and the strength of the electric field. The product of th e mobility and the lifetime is calculated for various samples; the res ults range from (3.4-2.5)X10(-8) to 4.2X10(-4)-1.6x10(-6) cm holes, re spectively. The carrier lifetime is found as a function of the illumin ation intensity. (C) 1994 American Institute of Physics.