In-situ Raman Spectroscopy on III-V semiconductors at high temperature in MOVPE

摘要

Through the implementation of a Raman spectroscopic equipment into a metalorganic vapor phase epitaxy setup (MOVPE) via optical fibers we determine surface and bulk related properties of III-V semiconductors in a temperature range up to 1200 K. Surface damages due to high temperature are avoided by a stabilization with gaseous group V elements which allows for reproducible measurements. The temperature dependent changes are monitored and analyzed through the change in the vibrational properties which are sensitive indicators of the sample and surface status. The results can be grouped into two categories: (i) irreversible changes with temperature (crystal quality, doping) due to sample annealing during the measuring process at high temperatures, and (ii) anharmonic effects (reversible) on phonon frequencies and line widths. We show that the TO and LO-phonon shifts at high temperature can be described well including fourth order phonon decay. The maximum temperature which can be reached is at present only limited by the subscale heating system.