The Study of As‐ and Sb Diffusion in Indium Melt

Abstract

The investigation of diffusion processes in metallic melts is of great interest for liquid phase epitaxial development. However, there has not been until now reasonable concordance between experimental data on diffusion coefficients even for the most studied semiconductor systems. Evidently, this is connected with indirect approach to the solution of the diffusion problem. According to such an approach the calculation of diffusion coefficients is performed as a rule using the kinetic characteristics of solution or crystal growth of binary compounds in a melt. GOROKHOV et al. have pointed out three independent experimental possibilities for determining the impurity concentration profile : the electron probe microanalysis, XRSFA and phase transition temperature (PTT) technique. As has been stated all the results were in a good agreement with analytical dependencies of Gap-Ga and GaAs-Ga systems.I n the present paper the results on determination of As-and Sb diffusion coefficients temperature dependencies in In melt in the temperature ranges of 873-1227 K and 628-873 K are given. The diffusion coefficient has been found using concentration profile of As (or Sb) that has been formed during the diffusion annealing in indium melt followed by tempering a t liquid nitrogen temperature. The experimental cell was a quartz capillar of 0.8-2.0 mm in diameter and 00 mm long filled with indium melt. On the melt surface the impurity source InAs (or InSb) single crystal was placed. The mass of the source was taken for the diffusion condition from an infinitely thin layer into semiinfinite volume t o be correct. Such niodel allows us to eliminatc the limiting influence of interface phenomena of the impurity compound solution. After diffusion annealing the concentration profile was fixed up by tempering of the melt at liquid nitrogen temperature. The measurement of impurity content along the capillar axis was performed with XRSFA on fluorescent spectrometer VKA-2 (Carl Zeiss-Jena) using Cr anode. Before the measurement the original sample was cut in 8-13 probes. The length of each was 2-5 mm. The impurity concentration in each probe was estimated by a number of X-ray pulses during 20-100 s. ASK, and SbL, lilies were used for As-arid Sb analysis, respectively. BOURRET et al. have reported about unsuccessful attempts to use XRSFA for studying impurity diffusion in a capillar that was clue to small square of a sample uiider radiation. To solve the similar problem i n our caHe each probe was rolled for preparing a film sample with square under radiation of 1.5-2.0 om3. h e to high elasticity of indium this operation can be quite easily performed. The temperature dependeiicies of As-and Sb diffusion coefficients in indium melt obtained usiiig the technique described above are show11 in Figures 1 and 2. The impurity diffusion coefficients obtained using YTT-technique and others iiivestigation methods are also given in these figures.One can see that experiniental dependencies are possible t o be described by Arrhenius law that is: D = Do...