Fortes efeitos de interfaces não-abruptas em poços Si/SiO2

Abstract

A model is proposed to describe simple Si/SiO₂ wells with nonabrupt interfaces. It is used to investigate how the existence of interfacial transition layerschange the carriers ( electrons and holes) energy levels in simple nonabrupt Si/SiO₂ wells. The numeric calculations are performed considering the space dependence of the carriers effective masses in the interface regions. It is obtained that the carriers energy levels iri simple nonabrupt Si/SiO₂ wells are blue shifted strongly if compared with those calculated for similar simple Si/SiO₂ abrupt wells. The results show that is not possible to estimate values for the carriers confinement potential in Si/SiO₂ wells using the abrupt interface picture to explain experimental data. Comparing the luminescence peaks dependence on the a - Si/a - SiO₂ well widths (as measured by Zu, Lockwood and Baribeau, Nature 378, 258 (1995)) with the electron-hole recombination energy calculated with the nonabrupt model for the wells, it was possible to suggest that the hole mass in the SiO₂ is 10 mg, where mo is the electron mass in the vacuum. When an electric field is applied to single Si/SiO₂ nonabrupt wells, it is shown that the carriers bound states Stark shifts tlepend strongly on the well interfaces width. They are always negative for the ground state and positive for the excited states, but for the latter it can turn to be negative de:pending on tlie electric field intensity, and on the width of the confinement wells and their interfaces. The performed research indicates the need of interface characterization in Si/SiO₂ wells to help the improvement of devices projects based on them.