| Popis: |
This chapter discusses the composition and sources of air-formed surface contamination with reference to the III–V surface reactivity and composition. The chapter stresses that nascent III–V surfaces become contaminated on exposure to air, no matter how brief the exposure time. This exposure results in a surface of complex composition containing hydrocarbons, native oxides, OH groups, metal bonds, and a loss of stoichiometry. Incorporation of the contaminated layer into interfacial regions during device processing can degrade the intended interfacial properties. The chapter assesses in-situ contamination removal techniques are and addresses the necessity for surface passivation to reduce contamination of the semiconductor surface during air exposure. This includes two levels of passivation. The first of these is a UV/ozone-formed thin, uniform, stoichiometric native oxide. The second passivation layer can be obtained by using hydrofluoric acid to remove the stoichiometric ozone-formed native oxide. The oxide affords protection of the semiconductor surface and, by careful control of thickness, can be compatible with many semiconductor processing steps. Using the experimental results obtained from different surface treatments standard surface preparation procedures are developed which can be used prior to most III–V interface engineering processes. |
