In situ thermal nitridation of GaAs using metalorganic vapor phase epitaxy

Abstract

The in situ thermal nitridation of GaAs surfaces has been performed by annealing GaAs in an ammonia ambient within a metalorganic vapor phase epitaxy (MOVPE) system. The shift of the GaAs surface Fermi level, and hence the surface charge density, resulting from the in situ thermal nitridation 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 determination of the surface Fermi level position. These structures were grown by MOVPE and in situ thermal nitridation was performed after growth within the MOVPE system without exposure to air. After nitridation, the surface Fermi level can be shifted by ∼0.23 eV towards the conduction band edge for UN + structures and by ∼0.11 eV towards the valence band edge for UP + structures from the normally mid-gap `pinned' positions. The surface morphology of nitrided surfaces was determined by atomic force microscopy (AFM).