TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY STUDY OF P2S5/(NH4)2S-TREATED AND ULTRAVIOLET OZONE-TREATED GAAS

Time-of-flight secondary ion mass spectrometry has been applied to the characterization of P2S5/(NH4)2S-treated and ultraviolet (UV)/ozone-oxidized GaAs (100) surfaces. Emphasis is placed on investigating the structural and chemical characteristics of the UV/ozone-induced oxide. Negative ion mass spectra obtained from passivated and UV/ozone-treated GaAs surfaces showed the presence of an arsenic-oxide-rich top layer with traces of S. Shallow depth profiling through the topmost layers indicated the presence of a gallium-oxide-rich layer under the arsenic-oxide-rich layer in samples exposed to UV/ozone for 15 min or longer. The gallium-oxide-rich layer also contained traces of S. The growth of the gallium-oxide-rich region is directly related to the time spent in the UV/ozone oxidation step.