Epitaxial CuGaSe₂ Thin Films − Removal of Cu_2−xSe Secondary Phase From Film Surface

Abstract

Cu‐rich CuGaSe2 (CGS) thin layers were prepared on GaAs (100) and stepped GaAs (111)A substrates by molecular beam epitaxy (MBE). The presence of a Cu/Cu2−xSe binary phase was observed and verified by XPS/UPS. By annealing the CGS samples subsequently at 600 °C growth temperature for 10 min, the secondary phase was removed while the Cu/Ga ratio decreased to a near stoichiometric value. Thus, the annealing step causes a reformation of the surface and surface structure, which could also be observed by LEED. Thereby the prior (4 × 2) reconstruction of the zinc blende order for the CGS [001] direction becomes sharper and more pronounced after the annealing step. For the [112] direction a (1 × 1) chalcopyrite reconstruction prior to the annealing step was changed into a clear (3 × 1) reconstruction after annealing the sample.

CuGaSe2 Thin Film Solar Cells: Challenges for Developing Highly Efficient Wide‐Gap Chalcopyrite Photovoltaics

“…These observations have been attributed to the smaller diffusion coefficient of elemental Ga compared with In, as well as the different structures of In 2 Se 3 (hexagonal) and Ga 2 Se 3 (cubic, Monoclinic, or orthorhombic) and the higher melting points of the Cu‐Ga‐Se material system. As can be seen in the Ga‐Se and Cu 2 Se‐Ga 2 Se 3 phase diagrams, Ga‐based materials have melting points which are typically about 100 °C‐higher than that of In‐based materials (In‐Se and Cu 2 Se‐In 2 Se 3 phases) . As a consequence, undesirable Cu‐Se secondary phases are often observed in CGSe and Ga‐rich CIGSe thin films when films are grown at the same substrate temperatures used for In‐rich narrow‐gap CIGSe films .…”

Effects of pressure on structural, mechanical, and electronic properties of chalcopyrite compound CuAlS2

“…Among ternary chalcopyrite semiconductors, CuAlS 2 has a direct wide band gap of 3.5 eV at room temperature, making it suitable material for the use of light emitting devices in the blue and blue green region [5][6] . Also, this compound was proposed to act as window material for cascade thin films solar cell to improve quantum efficiency with UV region [7][8] .…”