Model experiments on growth modes and interface electronics of CuInS sub(2): Ultrathin epitaxial films on GaAs(100) substrates

• Published in: Physica status solidi. A, Applications and materials science Vol. 211; no. 9; pp. 1981 - 1990
• Main Authors: Calvet, Wolfram, Lewerenz, Hans-Joachim, Pettenkofer, Christian
• Format: Journal Article
• Language: English
• Published: 01.09.2014
• Subjects: Banded structure; Copper; Electronics; Film thickness; Formations; Molecular beam epitaxy; Photoelectron spectroscopy; X-ray photoelectron spectroscopy
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201330429

The heterojunction formation between GaAs(100) and CuInS sub(2) is investigated using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). Thin layers of CuInS sub(2) films were deposited in a step-by-step process on wet chemically pre-treated GaAs(100) surfaces by molecular beam epitaxy (MBE) with a total upper thickness limit of the films of 60nm. The film growth starts from a sulfur-rich GaAs(100) surface. XPS core level analysis of the substrate and film reveals initially a transitory growth regime with the formation of a Ga containing chalcopyrite phase. With increasing film thickness, a change in stoichiometry from Cu-poor to Cu-rich composition is observed. The evaluation of the LEED data shows the occurrence of a recrystallization process where the film orientation follows that of the substrate with the epitaxial relation GaAs{100}||CuInS sub(2){001}. On the completed junction with a CuInS sub(2) film thickness of 60nm, the band discontinuities of the GaAs(100)/CuInS sub(2) structure measured with XPS and UPS were determined as Delta E sub(V)=0.1 plus or minus 0.1eV and Delta E sub(C)=0.0 plus or minus 0.1eV, thus showing a type II band alignment.