Abstract
This report presents results of research on electronic structure of three interfaces composed of organic layers of Alq3, Gaq3, or Erq3 deposited on GaN semiconductor. The formation of the interfaces and their characterization have been performed in situ under ultrahigh vacuum conditions. Thin layers have been vapor-deposited onto p-type GaN(0001) surfaces. Ultraviolet photoelectron spectroscopy (UPS) assisted by X-ray photoelectron spectroscopy (XPS) has been employed to construct the band energy diagrams of the substrate and interfaces. The highest occupied molecular orbitals (HOMOs) are found to be at 1.2, 1.7, and 2.2 eV for Alq3, Gaq3, and Erq3 layers, respectively. Alq3 layer does not change the position of the vacuum level of the substrate, in contrast to the other layers, which lower it by 0.8 eV (Gaq3) and 1.3 eV (Erq3). Interface dipoles at the phase boundaries are found to be −0.2, −0.9, −1.2 eV, respectively, for Alq3, Gaq3, Erq3 layers on GaN(0001) surfaces.
Highlights
Gallium nitride (GaN) is a very attractive semiconductor for applications in optoelectronics and photovoltaics
An important issue in the context of such systems is the electronic structure of the interface, in particular the interfacial polarization or the position of the highest occupied molecular orbital (HOMO) level of molecules relative to the valence band maximum (VBM) of the substrate
The three Mq3/GaN(0001) systems were grown in situ by evaporation of molecules from quartz crucibles heated with thermal radiation
Summary
Gallium nitride (GaN) is a very attractive semiconductor for applications in optoelectronics and photovoltaics. An important issue in the context of such systems is the electronic structure of the interface, in particular the interfacial polarization or the position of the highest occupied molecular orbital (HOMO) level of molecules relative to the valence band maximum (VBM) of the substrate. This information has been omitted in reports on Mq3 films on GaN(0001) surface. The tuning effect of central atom M in Mq3 molecules on the band offset is of application importance
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