Structural and optical characterisation of CuGaS2 thin films grown by MOVPE

Epitaxial growth of CuGaS2 using atmospheric pressure metalorganic (MO) vapour phase epitaxy (MOVPE) was carried out using two different copper metalorganic precursors, namely, cyclopentadienyl copper triethylphosphine (CpCuTEP) and hexafluoroacetylacetate copper triethylamine (Cu(hfac)2·NEt3). A change in the Cu content (most significant for epilayers grown using the former precursor) was found to occur along the flow direction. A study using X-ray diffractometry could not conclusively determine which of the possible structure types were present in the epilayer. Analysis of the transmission electron diffraction (TED) patterns using the <211> zone axes indicates that a mixture of disordered zinc blende and CuPt-type ordering occurs in both types of epilayers, whereas a tetragonal crystal structure (chalcopyrite or CuAu-type ordering) likely occurs within surface crystallites found in epilayers grown using Cu(hfac)2·NEt3. The photoluminescence (PL) for both epilayers consisted of a broad band at 580-620 nm, typical of Ga-rich material.