Materials Research Society Symposium Proceedings 468, 81 (1997).
Below is the abstract submitted to the meeting, not the abstract of the published paper:
GaN and its alloys have received much attention as materials for fabricating bright blue and green light optoelectronical devices, especially LEDs and LDs. MOVPE has, by far, proven its suitability for the epitaxial growth of high quality GaN. Thermodynamics is a fundamental tool in the analysis of any crystal growth process. However, the typical thermodynamic analysis cannot be applied to the MOVPE growth of GaN, because of inert behavior of nitrogen and the slow decomposition rate of ammonia. A quasithermodynamic analysis of GaN grown by MOVPE using TMGa and ammonia as source materials has been made. Equilibrium partial pressure as functions of input V/III ratio has been calculated. Phase diagram for the MOVPE growth of GaN is proposed, based on the quasi thermodynamic equilibrium model. In the phase diagram for the MOVPE growth of GaN, the four regions divided by the gallium forming line and etching line are: single solid GaN phase, GaN(s)+Ga(l) double condensed phase and two etching regions. In one of the etching regions Ga droplets appear on the surface during etching, in another region Ga droplet do not appear. No group V element condensed phase exists in the phase diagram. Epitaxial growth of GaN can only grow in the single condensed GaN phase. High input V/III ratio is needed to avoid the formation of gallium droplets on the growing surface. The calculation results show that the single condensed GaN phase region expands with decreasing growth temperature, reactor pressure, decomposition fraction of NH3, and fraction of hydrogen in a hydrogen-inert gas mixture carrier gas. The details of these effects will be presented.
This paper is part of Gallium Nitride and Related Materials II
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