Self-diffusion in indium antimonide and gallium antimonide

Abstract

Self-diffusion measurements have been made in the semi-conducting interrnetallic compounds InSb and GaSb. The material was single crystal or slightly polycrystalline. A tracer technique was used, in which layer's were removed from the crystal progressively and the residual activity in the crystal was counted after each section was taken. A hold-up on the surface of most of the radioactive tracer and the small magnitude of the diffusion coefficients limits the precision of the measurements and the temperature range over which they can be made with reasonable annealing times (a range of 40°C was used for both compounds). The data yield different diffusion coefficients for the group III atoms and the group V atoms in both compounds. The following values of D 0 and Q are obtained: D 9 (cm 2/sec) Q (kcal/mole) InSb In 0.05 41.8 Sb 0.05 44.6 GaSb Ga 3.2 × 10 3 72.6 Sb 3.4 × 10 4 79.4 The results allow the elimination of the following as possible mechanisms of self-diffusion in InSb and GaSb: 1. (a) direct interchange with nearest neighbors, 2. (b) a ring mechanism with equal numbers of group III and group V atoms in the ring, 3. (c) a vacancy mechanism with movements to vacancies in nearestneighbor positions only, 4. (d) interstitial diffusion in which the diffusing atoms always remain in interstitial positions or displace other atoms into an interstitial position if they re-enter the lattice. A reasonable mechanism for self-diffusion which accounts for the data in a consistent manner is vacancy diffusion in each of the face-centered cubic sublattices formed by the two constituents of InSb and GaSb. The product of grain-boundary width and grain-boundary diffusion coefficient in InSb was found to be 3.8 × 10 −16 cm 3 sec at 502°C. Diffusion of antimony in isolated dislocations in GaSb has been observed at temperatures near 700°C, with a product of diffusion coefficient and square of the dislocation radius between 10 −21 and 10 −22 cm 4/sec.