Flexible active-matrix electronic ink display U ltrathin, flexible electronic displays that look like print on paper are of great interest 1-4 for application in wearable computer screens, electronic newspapers and smart identity cards. Here we realize the fabrication of such a display on a bendable active-matrix-array sheet. The display is less than 0.3 mm thick, has high pixel density (160 pixels ǂ240 pixels) and resolution (96 pixels per inch), and can be bent to a radius of curvature of 1.5 cm
We report a study on Ge diffusion and its impact on the electrical properties of TaN∕HfO2∕Ge metal-oxide-semiconductor (MOS) device. It is found that Ge diffusion depends on the amount of GeO2 formed at the HfO2∕Ge interface and can be retarded by surface nitridation. It is speculated that Ge diffusion is in the form of GeO or Ge-riched HfGeO. Effective suppression of Ge diffusion by NH3 nitridation has resulted in improved electrical properties of TaN∕HfO2∕Ge MOS device, including equivalent oxide thickness (EOT), leakage current, hysteresis, and interface state density. The degradation of leakage current after high temperature post metallization anneal (PMA) is found to be due to Ge diffusion.
Metal-oxide-semiconductor field effect transistors (MOSFET) with a thin high-k dielectric were fabricated on bulk n-type germanium substrates. Surface oxides were thermally desorbed in situ by heating the substrates under ultrahigh vacuum conditions. First an ultrathin passivating layer was formed by evaporating germanium in the presence of atomic oxygen and nitrogen supplied from a remote radio frequency plasma source. Subsequently, the HfO2 dielectric was deposited by evaporating hafnium in the presence of atomic oxygen. An in situ TaN metal gate was similarly deposited. Long channel devices were fabricated using a standard process flow. These devices exhibited a low equivalent oxide thickness (EOT) of 0.7nm with gate leakage less than 15mA∕cm2 at VFB+1V. Device mobility was extracted from Is-Vg and split C-V characteristics. Results indicate a 2× mobility enhancement in Ge p-MOSFET devices compared to Si control devices. The demonstration of subnanometer EOT suggests that high-k gate dielectrics on germanium are scalable to low EOT and suitable for use in ultrascaled MOSFET devices.
Atomic layer deposition (ALD) was used to deposit passivating interfacial nitride layers between Ge and high-κ oxides. High-κ oxides on Ge surfaces passivated by ultrathin (1–2nm) ALD Hf3N4 or AlN layers exhibited well-behaved C-V characteristics with an equivalent oxide thickness as low as 0.8nm, no significant flatband voltage shifts, and midgap density of interface states values of 2×1012cm−1eV−1. Functional n-channel and p-channel Ge field effect transistors with nitride interlayer/high-κ oxide/metal gate stacks are demonstrated.
In this letter, we report successful fabrication of Germanium n-MOSFETs on lightly doped Ge substrates with a thin HfO 2 dielectric (equivalent oxide thickness 10 8 A) andTaN gate electrode. The highest peak mobility (330 cm 2 /V s) and saturated drive current (130 A/sq at -= 1 5 V) have been demonstrated for n-channel bulk Ge MOSFETs with an ultrathin dielectric. As compared to Si control devices, 2.5 enhancement of peak mobility has been achieved. The poor performance of Ge n-MOSFET devices reported recently and its mechanism have been investigated. Impurity induced structural defects are believed to be responsible for the severe degradation.
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