TRACE AND ULTRATRACE ANALYSIS OF GALLIUM-ARSENIDE BY DIFFERENT MASS-SPECTROMETRIC TECHNIQUES

The capability of different solid-state mass spectrometric methods [sp ark source mass spectrometry (SSMS), laser ablation inductively couple d plasma mass spectrometry (LA-ICP-MS), radiofrequency glow discharge mass spectrometry (rf GDMS) and secondary ion mass spectrometry (SIMS) ] in comparison with inductively coupled plasma mass spectrometry (ICP -MS) was investigated by the trace analysis of GaAs. For trace analysi s using solid-state mass spectrometry, a semiconducting laboratory GaA s standard (using high-purity GaAs) doped with Zn, B, Si, Ge, Sn, Sb, P, S, Se and Te (in the mu g g(-1) concentration range) was prepared b y the liquid encapsulation vertical Bridgeman technique. A selected pi ece of the synthetic laboratory GaAs standard was investigated directl y by SIMS, SSMS, rf GDMS and LA-ICP-MS. For the quantification of SIMS measurements single element ion-implanted GaAs certified reference st andards were used. After dissolution of the GaAs sample in high-purity HNO3-H2O2, the concentrations of the doped elements mere measured by ICP-MS and inductively coupled plasma atomic emission spectrometry (IC P-AES). By using the results of SIMS, ICP-MS and ICP-AES for the selec ted piece of the synthetic laboratory GaAs standard, relative sensitiv ity coefficients (RSCs) of the elements in SSMS, rf GDMS and LA-ICP-MS were determined. The experimentally determined RSCs were used for cor recting measured concentrations in an unknown GaAs sample. In order to reduce matrix effects in ICP-MS, a procedure for complete GaAs matrix separation in a chlorine-argon stream at 280 degrees C was evaluated. The recoveries of 24 elements after the chlorination of GaAs were det ermined to be nearly 100% (except for Sn and Ta), Ultratrace analysis of semiconducting GaAs after matrix separation was carried out by doub le-focusing sector field ICP-MS. The detection limits of ultratrace el ements in GaAs after matrix separation (in the tom ng g(-1) concentrat ion range) mere better by about one order of magnitude compared with m easurements without matrix separation and were comparable to those obt ained by solid-state mass spectrometry.