HfOx-based synapses are widely
accepted
as a viable candidate for both in-memory and neuromorphic computing.
Resistance change in oxide-based synapses is caused by the motion
of oxygen vacancies. HfOx-based synapses
typically demonstrate an abrupt nonlinear resistance change under
positive bias application (set), limiting their viability as analog
memory. In this work, a thin barrier layer of AlOxor SiOxis added to the bottom
electrode/oxide interface to slow the migration of oxygen vacancies.
Electrical results show that the resistance change in HfOx/SiOxdevices is more
controlled than the HfOxdevices during
the set. While the on/off ratio for the HfOx/SiOxdevices is still large (∼10),
it is shown to be smaller than that of HfOx/AlOxand HfOxdevices. Finite element modeling suggests that the slower oxygen
vacancy migration in HfOx/SiOxdevices during reset results in a narrower rupture
region in the conductive filament. The narrower rupture region causes
a lower high resistance state and, thus, a smaller on/off ratio for
the HfOx/SiOxdevices. Overall, the results show that slowing the motion of oxygen
vacancies in the barrier layer devices improves the resistance change
during the set but lowers the on/off ratio.