DETERMINATION OF MINORITY-CARRIER LIFETIMES IN CUINSE2 THIN-FILMS

We present detailed measurements of carrier lifetimes in CuInSe2 thin films. Time-resolved photoluminescence measurements are performed on p olycrystalline samples grown with a lateral gradient in the Cu/In rati o, thus enabling continuous evaluation of lifetime dependence on him c omposition. Luminescence at two distinct spectral positions is observe d: A high energy emission, attributed to free carrier or free exciton recombination (depending: on composition), that decays extremely fast with a lifetime of tens of picoseconds to a few ns; a lower energy emi ssion from defect related recombination that decays much more slowly, with typical lifetimes greater than tens of nanoseconds. We compare th ese results with results from CuInGaSe2 films. Radiative coefficients and minority carrier lifetimes are obtained from the data. (C) 1996 Am erican Institute of Physics.