The surface analysis of the solid state, (1)

SIMS (the secondary ion mass spectroscopy) has been applied for surface and interface analysis for solid sate materials, including semiconductors because it allows detection of all elements, surface analysis and depth profile measurement due to sputtering. It has also very fine detectability of impurities in the material down to 1013 atoms/cm3. In this report, a Camera ims-4f was employed to analyze silicon concentration in GaAs epitaxial layer grown by MBE (molecular beam epitaxy), MQW (multi quantum well) structures of AlGaAs/GaAs and selective doping in its structure, and GaAs thin layer by sputter deposition on the silicon oxide insulator. The silicon impurity concentration is determined down by 2.27 x 1015cm-3 while the lowest detectability which has ever been reported is about 2 x 1014cm-3 by T. Ambridge. The space resolution in the depth profile of an MQW is determined to be 50 angstrom in the present work while the value of the space resolution ever reported is elsewhere is about 20 angstrom. Quite high concentration of oxygen has been detected in the sputter-deposited GaAs layer on the SiO2 insulator. In addition to the works described above, the sputtering yield Y (=[the total atom number sputtered from the target]/[the total primary ion number injected into the target] of GaAs vs cesium primary ion or GaAs vs oxygen primary ion has been determined for some primary ion energy values. For cesium primary ion, two different values of Y are deduced. While a sputtering time between 1000 and 3600 seconds the Y of GaAs for 14.5 keV Cs+ primary ion with the primary ion current of about 2.0 x 10-8 A is about 5.0, the Y between 2000 and 3000 seconds sputtering time for 14.5 keV Cs+ primary ion with its current of about 2.0 x 10-9 A is 2.2. The reason of the difference of the Y values is not known. (author)