Surface composition changes in GaN induced by argon ion bombardment

Abstract

The wide-bandgap GaN semiconductor has been used to fabricate efficient blue-green light-emitting diodes, laser diodes and high-power/high-temperature electronic devices since the many problems regarding the life-time characteristics were resolved in recent years. Knowledge of ion-bombardmentinduced surface composition changes is important in quantitative AES/XPS analysis.We investigated the dependence of preferential sputtering of components on ion energies and on the angle of incidence of argon ions. Thin films of GaN prepared on a smooth Si substrate and GaN single crystals were bombarded with argon ions of energy 0.5-5 keV at incidence angles of 10-72• with respect to the surface normal. The N KLL and Ga LMM AES signals were acquired after the steady-state surface composition was reached. The results show that nitrogen is sputtered preferentially. This effect is more pronounced for higher ion energies and smaller incidence angles. The experimental results are discussed in the framework of models of preferential sputtering and compared with computer simulations.

Surface and in-depth characterization of InGaN compounds synthesized by plasma-assisted molecular beam epitaxy

“…The GaInN surface exposed to the 2 keV Ar + ion beam was found to be preferentially sputtered [41]. Such phenomenon was observed also for GaN, where the Ar ion bombardment caused preferential depletion of nitrogen from the surface [27,42], resulting in a Ga-rich surface. A preferred loss of In with respect to Ga can also be explained [43,44] by much lower bond energy of InN (7.7 eV/atom) than GaN (8.9 eV/atom).…”

Mg and Si dopant incorporation and segregation in GaN

“…Some of the samples studied with ESCA-microscopy were investigated before and after Ar þ ion sputtering. In order to avoid preferential sputtering of nitrogen [23], the ion energy was kept low, at 500 eV, and rather than normal ion incidence, a somewhat more grazing geometry with an incident angle of 458 was chosen. The mild sputtering was performed in a preparation chamber directly attached to the UHV analysis chamber.…”

Core-level photoemission and near-edge x-ray absorption fine-structure studies of GaN surface under low-energy ion bombardment

“…This shift indicates further decrease in coordination of Ga atoms, created by the preferential removal of nitrogen at these energies. 9 Removal of additional electronegative N atoms from Ga-N bonds creates less displacement of Ga valence electrons and provides the lower binding energy for Ga core electrons. At the same time, the Ga 3d emission exhibits an additional peak E1, shifted towards a lower BE by 1.44 eV.…”