Laplace deep level transient spectroscopy on self-assembled quantum dots

Self-assembled InAs quantum dots in a GaAs matrix are studied by Laplace deep level transient spectroscopy (LDLTS). This technique is demonstrated to be complementary to the well-established capacitance spectroscopy concepts and is particularly well suited for characterization of quantum dot layers with large separations from conductive layers. In comparison to conventional deep level transient spectroscopy, LDLTS can also be applied in the tunneling regime where the lifetimes of the confined states are independent of temperature, while in the thermal regime, LDLTS has a superior selectivity. The problems encountered hitherto with this technique are demonstrated to originate from the ill-posed character of the inverse Laplace transform and can be solved by a properly adapted choice of the regularization parameter.