At FCMN 2019 in Monterey California, Active Layer Parametrics will present mobility and activation depth profiles for Si:GaAs with a depth resolutions of <2nm through a film thickness of 150nm. Data was collected using the ALPro-50 DHEM profiler from a GaAs-on-Si wafer. Data provides direct activation profiles which correlates well with chemical compositional profiles captured by SIMS.