Characterization of InGaAsP materials by ultrahigh intensity post-ionization mass spectrometry: Relative sensitivity factors for zinc versus bulk constituents

Abstract

The first relative sensitivity factors (RSF) for detecting the major and dopant elements of optical materials by ultrahigh intensity post-ionization (UHIPI) mass spectrometry are determined. The post-ionization is performed using a single laser wavelength with intensities greater than 1014 W/cm2. Zn-implanted InP and In0.4Ga0.1As0.3P0.2 are used to investigate the photoionization of sputtered atoms and molecules. Under optimal conditions, the UHIPI RSF's for atomic singly charged In, Ga, and Zn are nearly equal; that is, the ratio of UHIPI signals is equal to the concentration ratio. In principle, no standards are needed for quantitative analysis. Arsenic and P, with higher ionization potentials, are not detected as efficiently as other elements. The detected mass balance is usually group III rich. An entire mass spectrum is necessary for complete characterization of all elements and adjustment of their RSF's because many sputtered molecules are detected containing the group V elements. Multiply charged species compose about 10% of the detected ions.