Room-temperature nitridation of gallium arsenide using alkali metal and molecular nitrogen

Synchrotron-radiation photoemission spectroscopy is used to investigate the room-temperature adsorption of molecular ${\mathrm{N}}_2$ on GaAs(110) surfaces modified by rubidium overlayers. While the clean surface remains unaffected by ${\mathrm{N}}_2$ exposures, the Rb-covered surface was found to exhibit nitride formation on both anion and cation sides with formation of much higher nitridation states for the Ga nitrides than by direct plasma nitridation. In contrast to the catalytic nitridation of silicon, reaction between the adsorbate and the surface is found to play a crucial role in the observed nitridation, which stresses the importance of surface defects.