Effect of Cd and Te2 Vapor Phase Mixture in CMBD on Growth Rate and Morphology of CdTe Films for Use in Thin-Film Solar Cells

We have developed revolutionary novel and nonvacuum and low cost chemical molecular beam deposition (CMBD) method in the atmospheric pressure gas flow for fabrication of II-VI binary, ternary and multinary films. CdTe films with different compositions were fabricated by this CMBD method in the atmospheric pressure hydrogen and argon flows using Cd and Te granules of 99.999% purity as precursors. The films were deposited at the substrate temperature of 500 °C. The growth rate varied in the wide range of 0.2-30 Å / sec. The composition of CdTe films were controlled by changing the molecular beam intensities (MBI) ratio of Cd and Te (evaporated amount). Samples were deposited on glass substrates. Under atmospheric pressure hydrogen flow we succeeded in obtaining stoichiometric (Cd / Te = 1.0) as well as p (Te rich)- and n-CdTe (Cd rich) films. The film thickness was 1.5 μm. Surface morphology of CdTe films was examined by SEM. The as deposited films contain high density and very well oriented cubic polycrystalline grains with the average grain size of 8 – 10 μm at high growth rates of 20- 30 Å / sec and nanocrystalline films at low growth rates of 0.2- 1 Å / sec.