Field-effect transistors with LaAlO3 and LaAlOxNy gate dielectrics deposited by laser molecular-beam epitaxy

Abstract

High permittivity LaAlO3 (LAO) and LaAlOxNy (LAON) thin films have been deposited directly on a Si(100) substrate using a laser molecular-beam epitaxy technique. Metal–oxide–silicon field-effect transistors (MOSFETs) are fabricated using such LAO and LAON thin films as gate dielectrics and well-behaved transistor characteristics have been observed. High-resolution transmission electron microscopy observations indicate that LAO thin films can remain amorphous structure even after annealing at 1000°C. The small equivalent oxide thickness (EOT) of 17Å is achieved for 75Å LAO film with an effective dielectric constant of 17.2±1 for the whole gate stack. Furthermore, a smaller EOT, larger drive current, and lower subthreshold slope have been observed for devices with the LAON thin film. For all the devices, the gate leakage currents are at least two orders of magnitude lower than that of the same electrical thickness SiO2. Reasonable subthreshold slopes of 248 and 181mV∕dec were obtained for MOSFETs with LAO and LAON films, respectively.