REPEATABILITY OF SI CONCENTRATION MEASUREMENTS IN SI-DOPED GAN FILMS

In high mass resolution secondary ion mass spectrometry Cs+ depth prof ile measurements of Si in GaN films, the secondary ion intensity ratio of Si-28(-) to the matrix Ga-69(-) signal has been observed to be poo rly repeatable from measurement to measurement. In some cases the Ga-6 9(-) signals from adjacent areas showed different intensity levels eve n though the Si-28(-) intensities were similar. Variation of the Ga-69 (-) matrix signal from run to run creates a large uncertainty in the d etermination of the Si concentration in a GaN film when a relative. se nsitivity factor is used. The changes in Ga-69(-) intensity from repea t measurements have been determined to be affected by the instrument v acuum condition, ion energy distribution, sample charging, and type of sample holder used in the measurement. (C) 1997 American Vacuum Socie ty.