The total pressure of arsenic over molten gallium arsenide at 1260°C

• Published in: Journal of crystal growth 1994-03, Vol.137 (1), p.255-258
• Main Author: Matthiesen, D.H.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Theory and models of film growth
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(94)91281-5

In the design of Bridgman type growth systems for the growth of GaAs, the use of a hermetically sealed fused quartz ampoule is often required. In addition, if the sample id to be directionally solidified in some manner, the melt is usually held at a temperature above the melting point of 1238°C, such as 1260°C. The literature generally supports the value of 0.97 atm for the total pressure of As over molten GaAs at the melting point, although there is not agreement on the ratio of the As 2 and As 4 species. However, only Richman [J. Phys. Chem. Solids 24 (1963) 1131] lists any data for the total pressure of aresenic over GaAs at temperatures above the melting point. His data indicate a value of 1.2 atm at 1260δC. In this paper several experiments are reported, which were conducted using a pressurized furnance and any subsequent deformation of the fused quartz ampoule, which at 1260δC is in viscous flow, was observed. Thus, for no deformation of the ampoule to occur, the internal ampoule pressure due to the total pressure of arsenic over the molten GaAs must be balanced by the externally applied pressure. Based on the results of these experiments, a value of 2.2 atm (18 psig) was measured for the total pressure of arsenic over molten GaAs at 1260δC. The value was used to construct ampoules for several different growth systems, all of which yielded successful ampoules with no deformation.