Deposition of CaF2 and GaF3 on sulfur passivated GaAs(111)A, 100, and (111)B surfaces

Abstract

The interfacial chemical bonding has been investigated for GaF3 and CaF2 deposited on S passivated GaAs(111)A, 100, and (111)B surfaces. Synchrotron radiation excited photoelectron spectroscopy S 2p measurements indicate greater S surface segregation for the Ga terminated (111) A and (100) surfaces relative to the As terminated (111)B surface. This S surface segregation correlates well with the Ga—S bond strength as well as the S—Ga coordination number for the three different GaAs surfaces. X-ray photoelectron spectroscopy measurements indicate S may act as a catalyst in the reduction of Ca2+ to metallic Ca at the CaF2–S/GaAs(111)A interface. In contrast to island growth observed for the CaF2/S/GaAs system, more uniform growth is observed for the GaF3/S/GaAs system. In addition, in contrast to the CaF2/S/GaAs system, band bending is considerably reduced for all surfaces upon deposition and annealing for the GaF3/S/GaAs system.