Bandgap variation in semiconductor thin films of the solid solution (CdTe)1-x(In2Te3)x deposited by RF sputtering

Abstract

(CdTe)1-x(In2Te3)x films, with 0.1 ≤ x ≤ 1, were deposited by radio frequency sputtering on glass substrates employing different targets, prepared for each composition. The x-ray diffractograms were consistent with substitutional In incorporation into the CdTe lattice up to a value of x = 0.2. For higher In contents, the films presented structural disorder without reaching full amorphous characteristics. For x = 1, corresponding to In2Te3, preferential growth was observed. The bandgap of the solid solution varied between 1.46 and 1.2 eV, reaching a maximum of 1.58 eV for x = 0.3. For both end binary compounds the random incorporation of a third chemical element produced a significant broadening of the Raman modes consistent with a reduction of the lifetime of the optical phonons. The electrical resistivity was dependent on the Cd concentration reaching a minimum for x = 0.8.