Thermodynamic Analyses of Open Tube Germanium Disproportionation Reactions

Abstract

In order to define conditions most suitable for iodine transport of pure or gallium doped germanium, the equilibria that obtain when these elements, singly or together, are mixed with iodine or hydrogen iodide in the presence of hydrogen and/or inert gases were analyzed using computer techniques. It was found that Ge in the presence of an inert carrier gas should transport via a hot to cold process at all iodine pressures studied. These results are markedly perturbed when H2 is substituted for the inert gas due to the establishment of a competing equilibrium whose enthalpic change is opposite in sign to that of the equilibrium responsible for semiconductor transport. The effects of the competing equilibrium in turn may be modified by using a mixture of H2 and He. Under certain sets o,f conditions, in fact, temperature insensitive regions develop which appear to be suitable as semiconductor source and seed sites. The results for the gallium-iodine equilibrium are to a good first approximation independent of the nature of the carrier gas and indicate that hot to cold transport is to be expected over a wide range of iodine concentrations. Analyses of the three phase equilibrium in Ge-Ga-halogen systems show them to also be independent of the nature of the carrier gas. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.99.31.134 Downloaded on 2015-05-14 to IP Vol. 111, No. 10 GERMANIUM DISPROPORTIONATION REACTIONS 1155 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.99.31.134 Downloaded on 2015-05-14 to IP Vol. 111, No. 10

Transpiration Studies of the Ge-I2-Inert Gas System

“…Two series of transpiration experiments w e r e conducted, one with an iodine source at 50.5~ the other with the iodine source at 61.8~ At all flow rates up to approximately 0.9 1/min, the systems appeared to be in equilibrium. 1 The calculated vapor pressures for the two temperatures were 2.14 _+ 0.06 m m and 4.79 ___ 0.07 ram, respectively. Comparison of these approximate values with those of B a x t e r and Grosse (3) the value of the vapor phase component mole ratio Ge/I2 as a function of temperature is limited at the lower temperature by a value of 0.5 coinciding with the semiconductor-halogen species stoichiometry GeI4.…”

Anomalous Thermal Behavior of Boron-Doped Low-Temperature Ge Epitaxial Layers

“…Purification of the carrier gas, preparation of the substrates, and the use of a vacuum chuck substrate holder to protect the surface during Ge deposition have been described in detail previously, as have a number of general considerations regarding the lowtemperature disproportionation reaction (1)(2)(3)(4).…”

Growth Mechanism of Vapor Deposited Germanium Films

“…A number of studies of systems including Ge-I2-H2-He-HI have been made (10)(11)(12)(13)(14), but the results of these studies are not necessarily applicable to the physical system employed in the present investigation. A number of studies of systems including Ge-I2-H2-He-HI have been made (10)(11)(12)(13)(14), but the results of these studies are not necessarily applicable to the physical system employed in the present investigation.…”

“…In order to determine the operating conditions under which equilibrium is achieved in the open-tube flow system used in this work a transpiration study was initiated whereby weight-loss measurements were employed to determine the pressures of various gaseous species formed at the iodine and germanium sources for the system Ge-I2-H2. A number of studies of systems including Ge-I2-H2-He-HI have been made (10)(11)(12)(13)(14), but the results of these studies are not necessarily applicable to the physical system employed in the present investigation. Measurements were made as a function of iodine and germanium source temperatures and gas flow rate.…”