[en] The electronic properties of a self-assembled Ga Sb/GaAs QD ensemble are determined by capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS). The charging and discharging bias regions of the QDs are determined for different temperatures. With a value of 335 (±15) meV the localization energy is rather small compared to values previously determined for the same material system. Similarly, a very small apparent capture cross section is measured (1.10"-"1"6 cm"2). DLTS signal analysis yields an equivalent to the ensemble density of states for the individual energies as well as the density function of the confinement energies of the QDs in the ensemble.