The fundamental surface science of wurtzite gallium nitride

Electronic properties of air-exposed GaN(11-00) and (0001) surfaces after several device processing compatible cleaning steps

“…The surface BB can be directly extracted from the binding energy (BE) of the valence band maximum (VBM), although with a mediocre precision due to the difficulty to accurately fit the valence band onset [32]. Instead, similarly to the method advocated by Bermudez [18], we measure the binding energy of the Ga 2p 3/2 core level (BE Ga 2p3/2 ) and relate it to the surface BB through:…”

“…To overcome these issues, surface cleaning can be used to reinitialize at will air-exposed surfaces into a predefined state. A wealth of cleaning methods has been developed, as reported in the extensive and detailed article of Bermudez [18]. The author concludes by advocating the use of cleaning steps performed in situ under high vacuum conditions -annealing above 500 • C under Ga or NH 3 fluxes and/or N ion sputtering -to reproducibly obtain GaN surfaces free of adsorbates and with a well-defined atomic order.…”

Complex Geometric Structure of a Simple Solid-Liquid Interface: GaN(0001)-Ga

“…An empirically found recipe, consisting of heating under a controlled nitrogen atmosphere, was used to optimally contact the liquid gallium with the substrate [8]. This procedure repairs the surface and cleans residual impurities [14], resulting in a well-defined and atomically smooth interface at near-equilibrium conditions at the nitrogen pressures used.…”

Towards simulation at picometer-scale resolution: Revisiting inversion domain boundaries in GaN

“…However in this case, an even number of IDB has to be introduced in the supercell, usally two IDB and two crystalline grains. In the second case, studies with free surfaces parallel to an interface are usually done with full periodic conditions while inserting a vacuum layer between the surfaces 20,24 . The width of the vacuum must minimize as much as possible the interaction through the empty space of the atoms at the surfaces.…”

“…Instead of the two interacting IDB -due to the artificial periodicity perpendicular to the interfaces -there are now possible interactions between one IDB and the free surfaces parallel to it (configurations shown in figures S12 and S13 in Supporting Information 30 ). The initial surfaces has been obtained by truncating the lattice perpendicularly to the [11 0 0] direction and are therefore non polar 24 (see figure S10 in Supporting Information 30 ). No external atoms have been added at these (11 0 0)-surfaces to passivate them, in order to get the clean-surface effects.…”