The zirconium-doped hafnium oxide (ZrHfO) high-k thin film has excellent gate
dielectric properties, such as a higher crystallization temperature, a lower defect density,
and a larger effective k value. As a promising high-k material, ZrHfO has been utilized for
both nonvolatile memory (NVM) and light emitting applications. Replacing the
polycrystalline Si floating gate, the discrete nanocrystals embedded ZrHfO gate dielectric
can achieve promising NVM performance. On the other hand, warm white light can be
emitted from the thermal excitation of nano-resistors form from the dielectric breakdown
of the ZrHfO Metal-Oxide-Semiconductor (MOS) capacitor. This novel solid state
incandescent light emitting device (SSI-LED) unveils a new concept for the lighting
device evolution.
Nanocrystalline cadmium sulfide (nc-CdS) embedded ZrHfO high-k NVMs have
been fabricated to reduce the frequency dispersion problem caused by defects at the
nanocrystal/dielectric interface. The nc-CdS embedded device can retain about 53% of
originally trapped holes for 10 years and exhibit outstanding memory function at low
operation voltage. The study on the nc-CdSe embedded ZrHfO NVMs shows that the high
temperature enhances the hole trapping but decreases the electron trapping. Based on the
different temperature dependences, the stored electrons release faster than stored holes.
The raised temperature accelerates the dielectric breakdown process by increasing defect
densities and defect effective conduction radii.
The post deposition annealing (PDA) atmosphere is critical to the electrical and
light emission characteristics of ZrHfO SSI-LEDs. It affects the dielectric breakdown,
light emission intensity and efficiency by changing compositions of the high-k stack and
the nano-resistor. The electrical properties, i.e., effective resistances and Schottky barrier
heights of nano-resistors have been estimated. The nano-resistor behaves neither like a
conductor nor like a semiconductor. Moreover, the barrier height inhomogeneity is
observed due to the random and complicated nano-resistor formation. The embedding
method and the heavily doped p-Si substrate have been employed to enhance the light
emission from ZrHfO SSI-LEDs.
Lastly, extensive applications of this novel nano-resistor device for on-chip optical
interconnects and as diode-like anti-fuses have been discussed
