Real-time monitoring of MOVPE device growth by reflectance anisotropy spectroscopy and related optical techniques

Reflectance anisotropy spectroscopy (RAS/RDS) so far has been mostly used for basic growth studies in both molecular beam epitaxy (MBE) and metal-organic vapor-phase epitaxy (MOVPE). Due to its sensitivity to the uppermost atomic monolayers, RAS became a very versatile tool for investigating surface stoichiometry, surface reconstruction and surface morphology especially under gas-phase conditions. Meanwhile, however, the performance and adaptability of RAS to standard MOVPE systems has been enhanced significantly and RAS sensors now can also be used for MOVPE device growth monitoring and control. Therefore, after a brief introduction to the basic surface physics and surface chemistry causing the optical signatures, this paper concentrates on device related applications. Examples will be given concerning the optical response to both n-type and p-type GaAs doping levels and the real-time measurement of ternary compound composition for reaching lattice matched growth. The optical surface response during the growth of a complete GaAs/InGaP heterojunction bipolar transistor is visualized. The result indicates on a monolayer level either consistency or deviation from the intended growth process. (C) 1998 Elsevier Science B.V. All rights reserved.