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

Abstract

Abstract At disordered Si/SiO 2 interfaces the lattice mismatching results in dangling bond P b 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 (1 0 0) and (1 1 1) interface orientations. The (1 1 1) distribution is 0.08 eV broad and centred at 0.38 eV below the silicon conduction band. This is consistent with only P b0 states being present. While for the (1 0 0) 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 (1 1 1) 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.