GROWTH MONITORING BY REFLECTANCE ANISOTROPY SPECTROSCOPY IN MOVPE REACTORS FOR DEVICE FABRICATION

Reflectance anisotropy spectroscopy (RAS) has proved its capability to study surface processes during metalorganic vapour phase epitaxy (MOV PE) growth of a variety of III-V compounds. However, these investigati ons up to now have been mostly restricted to specialized research reac tors. Therefore, we studied the feasibility of in-situ monitoring by R AS during growth on two production-type MOVPE reactors: horizontal 2 i nch single wafer reactor AIX 200 and Planetary Reactor(TM) AIX 2000 fo r 5 x 3 inch. The slight modifications of the reactors necessary to ga in normal incidence optical access to the sample do not alter the prop erties of the grown materials. While in the horizontal reactor the str ain-free optical window allows one to obtain well-resolved RAS spectra the signals in the multiwafer reactor are affected by the anisotropy of the ceiling plate. Even in this case RAS spectra can be extracted. First measurements on rotating samples in the horizontal reactor demon strate the possibility to obtain RAS spectra by multitransient spectro scopy. As an application monitoring of the growth of p-type layers for the base of GaInP/GaAs hetero-bipolar-transistors (HBTs) is discussed . The linear electro-optic effect (LEO) gives information on doping ty pe and doping level. Time-resolved transients at specific energies are used to study the impact of different switching schemes on the proper ties of the base-emitter interface.