Energy state distributions at oxide-semiconductor interfaces investigated by Laplace DLTS

摘要

At disordered Si/SiO_2 interfaces the lattice mismatching results in dangling bond P_2 centres forming a rather broad distribution of energy states. In this study these energy distributions have been determined using isothermal current Laplace deep level transient spectroscopy (DLTS) for the (100) and (111) interface orientations. The (111) distribution is 0.08eV broad and centred at 0.38eV below the silicon conduction band. This is consistent with only Pbo states being present. While for the (100) orientation this distribution is broader (0.1 eV) and deeper (0.43 eV) on the energy scale. Detailed studies revealed two types of the interface states in this broad distribution: one similar to the (111) orientation while the other has a negative-U character in which the emission rate versus surface potential dependence is qualitatively different from that observed for P_(b0) and is presumed to be P_(b1)-Discrepancies between P_b states energy distributions obtained with a use of the isothermal Laplace and conventional DLTS measurements are discussed. The presented experimental procedure can be used for analysis of interface states observed at interfaces of other semiconductor-oxide/dielectric systems.