Violation of the rate-window concept in the charge deep-level transient spectroscopy using second-order filtering

When applying the thermal-scan charge deep-level transient spectroscopy (Q-DLTS) utilizing second-order filtering to diamond- or GaAs-based Schottky-like diodes, we found correlated Q-DLTS signals which increased monotonically with temperature and did not depend on the rate window set at t(1)(-1). In accordance with the hyperbolic kinetics of the transient current in diamond films, the related transient charge Q(t) (integrated current), when correlated, is invariant for the rate window. Thermal activation energy of the transient current is easily deduced from the Q-DLTS experiment. Possible consequences for feedback-charge capacitance-voltage measurements, which may also be classified as second-order filtering in the time domain, are pointed out. One of them might be a sign reversal of the excess capacitance at short times of observation.