Tunneling spectroscopy of the GaAs(110) surface

The scanning tunneling microscope is used to study the spectroscopy of p-type, n-type, and oxygen-covered GaAs(110) surfaces. On the clean surface, three components of the current are identified—tunneling out of valence-band states, tunneling into conduction-band states, and tunneling through dopant-induced states in the semiconductor. The results are compared with a theoretical computation of the tunneling current, including band bending in the semiconductor. Good agreement between theory and experiment is obtained only when tunneling through the space-charge region of the semiconductor is included. On the oxygen-covered surface, the spectroscopic results show evidence of band bending due to the oxygen adsorbates.