In situ surface passivation of gaas by thermal nitridation using metalorganic vapor phase epitaxy

摘要

An ammonia-based, in situ passivation of GaAs surfaces conducted within a metalorganic vapor phase epitaxy reactor is present. The shift of the GaAs surface Fermi level, and hence the surface charge density, resulting from this in situ passivation, has been studied using photoreflectance (PR) spectroscopy. Samples consisting of an undoped GaAs layer on highly doped n-GaAs (UN~+) and p-GaAs (UP~+) structures allow for the exact determination of the surface Fermit level position using PR. These structures were grown by MOVPE and in situ thermal nitridation was performed after growth withint he MOVPE system without exposure to the air. After nitridation, the surface Fermi level can be shifted by approx 0.23 eV towards the conduction band edge for UN~+ structures and by approx 0.11 eV towards the valence band edge for UP~+ structures from the normally mid-gap 'pinned' positions.