THE FEATURES OF SCANNING LIQUID PHASE EPITAXY TECHNIQUE AS APPLIED TO THICK EPITAXIAL LAYERS GROWTH

Background. Growing of both thin and thick epitaxial layers is an essential part of semiconductor device technology. Liquid phase epitaxy is among well-known technological methods. There are pulse methods of liquid phase epitaxy specially developed for obtaining thin epitaxial layers. Their adaptation or modification for obtaining thick epitaxial layers is an actual issue. Objective. This work deals with the possibility of obtaining of thick epitaxial layers by extending the capabilities of scanning liquid phase epitaxy technique which also relates to pulse liquid phase growing methods. Methods. In this work we considered the influence of extra heating of the substrate on the growth of epitaxial layers when using scanning liquid phase epitaxy technique. For this purpose we carried out modelling of heat- and mass transport processes in the apparatus of scanning liquid phase epitaxy in conditions of extra heating of the substrate. To experimentally approve the validity of the model proposed we carried out the growing of Ge epitaxial layer on GaAs substrate in the above mentioned conditions. Results. The modelling showed that if the substrate was in contact with the solution-melt more than 1 second in conditions of substrate extra heating in scanning liquid phase epitaxy method, a segment of epitaxial layer dissolution appeared in plots of the grown epitaxial layer thickness against the growth time. The crystallization front temperature was lower than the initial solution-melt temperature in this case. We showed that it was connected with the magnitude of initial cooling/heating of the substrate heater. The modelling also showed that the epitaxial layer growth occurred in kind of a temperature gradient due to the extra substrate heating. Thus in a few seconds there took place the growth in the time-constant temperature gradient. Using the extra substrate heating we obtained epitaxial Ge layer on GaAs substrate from Ga-Ge solution-melt. The growth time was 60 sec. The layer thickness determined by spherical slice technique was 12.6 um. Conclusions. In this work we showed that using extra heating of the substrate’s back side there appeared the conditions for growing of thick epitaxial layers by scanning liquid phase epitaxy technique in case when the substrate temperature was lower than the solution-melt temperature. Here the growth of thick epitaxial layers took place in the condition of temperature gradient at crystallization front.