Hall-effect measurements were performed on Te-doped AlxGa1-xSb layers, which had been grown by molecular beam epitaxy, in order to investigate the compositional dependence of the DX center occupancy level. The samples had AlSb mole fractions such that x ranged from 0.25 to 0.50, and n-type doping levels of about 1018/cm3. Some samples with x = 0.40, and different doping levels (5 x 1015 to 1018/cm3), were also studied. Hall electron density versus temperature data were analyzed for temperatures above 150K, where the DX center was at equilibrium, by assuming a negative-U model for the DX level and by taking account of multi-valley conduction effects. The DX level, which was degenerate in energy with the conduction band at low x-values, entered the forbidden gap at x = 0.25 and then became deeper with increasing x-value. In lightly-doped samples, the introduction of a second level of the same Te impurity was required in order to fit the data. Such a level could be identified with the non-metastable level which controlled the low-temperature electrical properties.

Occupancy level of the DX center in Te-doped AlxGa1-xSb A.Baraldi, C.Ghezzi, A.Parisini, R.Magnanini, L.Tarricone, S.Franchi: Journal of Applied Physics, 1999, 85[1], 256-63