In-situ monitoring of the p- and n-type doping in AlGaInP

We investigated the effect of Mg p- and Te/Si n-type doping on the in-situ reflectance anisotropy (RAS) spectra for the material system AlGaInP. All results have been compared to ex-situ performed Hall abd SIMS measurements. RAS intensities of Mg-doped AlInP first increase with increasing Mg-flux and then decrease even below the level of the undoped spectra. We explain by the effect, that beyond a critical Mg-flux the excess Mg remains on the surface and causes roughening of the surface and decreasing of the RAS intensities. For the n-type dopants we found a very different impact on the RAS data for Te doping than for Si doping. The RAS intensities from the Si-doped layers show a linear dependence versus the logarithm of the free carrier concentration. The RA spectra of Te-doped samples show a significant change in the shape of the spectra, which is related to surfactant effect of tellurium accumulating on the surface. Besides this a clear dependence of the RA-features to the free carrier concentration was found.