High-precision characterization of III-nitride semiconductor alloys with secondary ion mass spectrometry (SIMS)

Samples 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 III-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 nonlinearities. 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%