HETEROEPITAXIAL GROWTH OF CUGAS2 LAYERS BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION

Heteroepitaxial growth of CuGaS2 was studied by low-pressure metalorga nic chemical vapor deposition using normal-tripropylgallium as a new G a precursor, combined with cyclopentadienylcoppertriethylphosphine and ditertiarybutylsulfide. Structural and optical properties were charac terized in detail. The epilayer showed the c[001]-oriented growth on b oth GaAs(001) and GaP(001) substrates. The lattice parameter c of the epilayers was smaller than that of the bulk single crystal. Magnitude of the residual lattice strain for CuGaS2/GaP(001) was found to be lar ger than that for CuGaS2/GaAs(001), even though the lattice mismatch f or the former was smaller than that for the latter. The strain is cons idered to be introduced during cooling after the growth. A photolumine scence peak at 2.493 eV (8 K) was assigned to a free exciton emission, because the peak energy agreed with A-exciton energy obtained from ph otoreflectance spectra.