Degeneracy factor and pressure dependence of Si-induced deep impurity states in AlxGa1-xAs from transport experiments under hydrostatic pressure

Deep electron traps (the so-called DX centers) have been studied by means of Hall and conductivity measurements under hydrostatic pressure, between 77 K and 500 K in n-type MBE grown Al.33Ga.67As doped with Si. From our measurements we can access quantities such as the net doping concentration and the mobilities in each valley of the conduction band. The knowledge of these parameters allows us to interpret the Hall carrier density over the whole temperature range without the use of fitting parameters. The value of the pressure coefficient is found to be equal to -11.5 meV/kbar with respect to the Γ minimum, in agreement with the value from the activated temperature range. Two sets of values for the temperature dependence and the degeneracy factor of the level are proposed. (author) 11 refs., 3 figs