Characterization of deep traps in semi-insulators by current transients

Deep traps in semi-insulators (SI) are characterized using a junction composed of an epitaxial p-type layer grown on SI n-type layer. At a reverse bias electrons are released from the traps resulting in a current transient through the substrate. Simultaneously the depletion region in the epilayer expands until the entire layer is depleted leading to a decaying epitaxial current. The analysis of these transients renders the electron emission and capture coefficients and lifetime, and the energy location of the traps. The long current decay are accelerated by illuminating the sample with photons of energy below the band gap, as long as their energy is larger than the difference between trap energy and the bottom of the conduction band. Thus we determined directly this energy difference.