Effects of a resonant shallow state on the electrical properties of Te-doped AlxGa1-xSb

In AlxGa1-xSb, the Te impurity originates a simple donor state (D level), whose occupancy equilibrates rapidly with the conduction band; it coexists with a DX state which is responsible for the persistent photoconductivity effect. The D level is linked to the L conduction band minima and becomes resonant with the conduction band for x<0.20. Under these conditions, occupancy variations in the D level give rise to a nonomonotonic temperature dependence of the n(H) Hall density which is not attributable to mixed conduction effects. The role of the D level was investigated in samples of different alloy compositions (x<0.20) and doping levels (10(16)-10(18) cm(-3)) and analyzed using a simplified model. The analysis confirmed the role of the occupancy variations in the D level in determining the temperature dependence of n(H) and the linkage of the level to the L conduction band edge.