AlGaAs composition measurements from in situ optical reflectance

We describe preliminary determinations of AlGaAs layer composition using in situ optical reflectance spectroscopy (ORS) data. RHEED oscillations are used to independently determine the composition of the AlGaAs layers. The results are compared with ex situ measurements. Although additional work is needed to refine the uncertainty estimates and reduce sources of error, we find that growth rate as measured by ORS agrees with RHEED oscillation data to within 2%. The ultimate goal of this project is to produce standard reference materials of certified alloy composition to mole-fraction uncertainty of 0.002 for a range of important III-V alloys.