Time-dependent response of interface states in indium phosphide metal–insulator–semiconductor capacitors investigated with constant-capacitance deep-level transient spectroscopy

Abstract

Constant-capacitance deep-level transient spectroscopy measurements performed on InP-SiO2 metal-insulator-semiconductor capacitors are reported for the first time. Two types of samples have been used, one of epitaxial InP with a free-electron concentration n=1.4×1015 cm−3 and covered with an ‘‘undoped’’ SiO2 insulating layer, the other of bulk material with n=1016 cm−3 and covered with an HCl-‘‘doped’’ SiO2 dielectric. Extensive experiments have been performed and a model has been proposed which successfully explains the corresponding results. This model is based on the assumption of a spatial and energetical distribution of interface states within the dielectric. The interaction of these traps with the conduction band takes place via a tunneling process during the capture of electrons and by a tunneling followed by a thermally activated transition during the emission process. The interface state density has been found to be about 1012 cm−2 eV−1 in the energy range between about 0.2 and 0.5 eV below the conduction band and to decrease considerably to the conduction band above about 0.2 eV. Thus accumulation can be reached. The interface state density strongly increases below about 0.6 eV for the undoped sample and about 0.7 eV for the HCl doped one. Thus strong inversion has not been observed. It is shown that the models presented previously are inconsistent with our experimental results while the model proposed in the present paper explains our and most of the experimental results given in the literature.