Using optical reflectance to measure GaN nucleation layer decomposition kinetics

In addition to directly fitting the reflectance waveforms, we introduce another way to quantify decomposition rates measured under constant or varying T. This approach requires a constant EA for the reaction kinetics throughout the entire T range of interest, which is the case for the GaN NL decomposition. For this approach, time is scaled by an integrated form of the Arrhenius exponential (i.e. exp(-EA/kBT)). We have called this transformation of the time scale the “kinetic advancement,” because it allows kinetic processes at constant or varying T to be compared directly. If the reflectance waveform or NL thickness is plotted vs. the kinetic advancement, a straight line results with the slope equal to A0. The usefulness of both reflectance waveform fitting procedures is discussed, specifically how the reflectance waveform can be compared and quantified during every growth run in order to verify NL evolution repeatability.