Segregation of tellurium in GaSb single crystals and associated diffusion coefficient in the solute layer

Exceptionally uniform, steady-state tellurium segregation was observed in a GaSb single crystal grown by the submerged heater method. The single cryst al was grown at 5 mm/h in a 20 mm diameter silica crucible using a 20 mm di ameter [1 1 1] B seed and with melt encapsulation by NaCl-KCl salt. The axi al dopant profile consists of three regions: an initial transient, a steady state uniform region and a last to freeze inhomogeneous portion. In the st eady state region, the dopant concentration is equal to the initial telluri um content (C-o) in the melt. The axial tellurium profile was best fitted b y the Tiller's equation for diffusion controlled segregation with k = 0.37 and D = 1.0 x 10(-5) cm(2)/s. The inhomogeneous composition in the last to freeze portion is caused by Marangoni convection which takes place after th e baffle separates from the melt. The electrical properties of the crystal were evaluated by Hall measurements and four-point probe technique. (C) 199 9 Elsevier Science B.V. All rights reserved.