In situ thermal nitridation of GaAs using metalorganic vapor phase epitaxy

The in situ thermal nitridation of GaAs surfaces has been performed by anne aling GaAs in an ammonia ambient within a metalorganic vapor phase epitaxy (MOVPE) system. The shift of the GaAs surface Fermi level, and hence the su rface charge density, resulting from the in situ thermal nitridation has be en studied using photoreflectance (PR) spectroscopy. Samples consisting of an undoped GaAs layer on highly doped n-GaAs (UN+) and p-GaAs (UP+) structu res allow for the determination of the surface Fermi level position. These structures were grown by MOVPE and in situ thermal nitridation was performe d after growth within the MOVPE system without exposure to air. After nitri dation, the surface Fermi level can be shifted by similar to 0.23 eV toward s the conduction band edge for UN+ structures and by similar to 0.11 eV tow ards the valence band edge for UP+ structures from the normally mid-gap 'pi nned' positions. The surface morphology of nitrided surfaces was determined by atomic force microscopy (AFM). (C) 1998 Elsevier Science B.V. All right s reserved.