Czochralski growth and characterization of GaSb

Abstract

Single crystal GaSb is important as a substrate for long wavelength ( ⩾ 1.5 μm) detectors and lasers. Procedures for the reproducible synthesis of GaSb, and Czochralski growth of single crystals with varied stoichiometry are discussed. The distribution of dopants including Te, Se, Si and Ge was studied and the dependence of carrier concentration on dopant concentration (determined by atomic absorption analysis) is reported. In the Te concentration range studied, 1.5 × 1017 -3 × 1019 cm-3, the carrier concentration is always substantially less than the Te concentration ranging from ≈ 0.25 at low Te to ≈ 0.14 at high Te. Room temperature electron mobilities > 3000 cm2 V-1 s-1 are obtained at low carrier concentrations. The interface shape and its change with fraction frozen is shown to affect the impurity distribution. Normal freeze behavior is qualitatively observed for Te partition as a function of fraction of melt frozen. Equations for the effect on impurity distribution of the changing Ga/Sb ratio in the solid as freezing proceeds are developed and compared with experimental results. It is shown that the most important correction to the distribution constant is based on interface shape changes and on and off facet growth as freezing proceeds.