A DETAILED HALL-EFFECT ANALYSIS OF SULFUR-DOPED GALLIUM ANTIMONIDE GROWN BY MOLECULAR-BEAM EPITAXY

Experimental data are presented for the Hall coefficient and the apparent Hall mobility over the temperature range 160-500 K for five samples of molecular-beam epitaxially grown sulfur-doped GaSb. The donor concentration of the different samples varied between 3.3×1017 and 7.5×1016 cm-3, and the native acceptor concentration between 8×1016 and 1.2×10 16 cm-3. The samples show a large spread in the apparent carrier activation energy. A two valley compensated conduction model is presented that shows that the variation in apparent carrier activation energy results from different compensation ratios in the samples. This model also shows that the constant value of the Hall coefficient observed at high temperatures is not due to donor exhaustion but carrier promotion to the lower mobility L1 band. Using constraints provided by secondary ion mass spectrometry and capacitance-voltage measurements on the samples, as well as growth data, it is shown that a narrow spread of values for the donor binding energy around 60 meV is required to account for the data. It is suggested that this spread is due to the formation of a donor band and to the strongly attractive central cores of the sulphur donors.