High-Precision Characterization of III-Nitride Semiconductor Alloys with Secondary Ion Mass Spectrometry (SIMS)

ABSTRACTSamples of representative AlxGayIn1−x-yN compositions have been studied with secondary ion mass spectrometry (SIMS). First, ionized species of common interest (H, B, C, O, Mg, Si, and Cd) were implanted into the Ill-nitride samples to provide calibrated standards. Depth profiles and conversion factors for quantification of dopants were then obtained using O2+ or Cs+bombardment and positive or negative SIMS to measure B+ and Mg+; H−, B−, C−, O−, and Si−; and CdCs+. In addition calibration curves for quantification of stoichiometry were prepared using MCs+ ions (NCs+, AlCs−, GaCs+, InCs+) for which the ion yields are relatively independent of the matrix composition; and using atomic, dimer, and trimer ions (Al, Ga, In, Al2, Ga2, In2, Al3, Ga3) which are very sensitive to matrix composition. The empirical calibration curves show small non-linearities. Dopant concentrations can be quantified with great sensitivity (detection limits usually below 1 ppm), accuracy (usually better than 10%), and precision (better than 25%). Matrix stoichiometry can be quantified with an accuracy of about 1–3%.