Increased sensitivity of SIMS in indium phosphide by detecting PxM− molecular ions under cesium bombardment

Abstract

Abstract Elements of group 2 (p-type dopants), of transition (Ti, Fe, Cu), and of groups 13 to 16, including n-type dopants, were implanted into (100) indium phosphide substrates at energies between 190 and 800 keV and to doses ranging from 1013 to 1015 atoms cm−2. These implants were studied by secondary ion mass spectrometry. The useful yields, background levels, and detection limits were measured for M−, InM−, and PxM− negative ions under cesium bombardment ( x going up to 6 and M representing the element of interest). It is found that, with a low mass resolving power, practically all the elements, except Mg and S, which are interfered with residual vacuum contaminants, may be analysed with detection limits ranging between 2 × 1014 and 5 × 1016 atoms cm−3. Furthermore, the high useful yields of the PxM− clusters make it possible to perform high mass resolving power experiments and, in this case, all the limits are lowered by one decade or more to be between 2 × 1013 and 2 × 1015 atoms cm−3 (1 × 1015 for Mg, 2 × 1015 for Zn and 2 × 1015 for S). The amounts of Ti, Cu, Al, Ge, Sn, Pb, and Sb are found to be less than or equal to 2 × 1014, 2 × 1015, 3 × 1014, 8 × 1013, 1 × 1014, 2 × 1015, and 1 × 1014 atoms cm−3, respectively.