J.-R. Yang

Band offsets and charge storage characteristics of atomic layer deposited high-k HfO2∕TiO2 multilayers

The band offsets and charge storage characteristics of atomic layer deposited high-k HfO2∕TiO2 multilayers with ten periods in p-Si∕SiO2∕(HfO2∕TiO2)∕Al2O3 structure have been investigated. The thickness of high-k HfO2 or TiO2 film is ∼0.5nm for each layer, before and after annealing treatment of 900°C for 1min in N2 ambient. High-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy measurements on high-k HfO2∕TiO2 multilayers confirm the layer-by-layer structure after annealing treatment, suggesting the HfO2∕TiO2 multilayer quantum wells. The valence band offsets of HfO2 and TiO2 films are found to be ∼3.1 and ∼1.5eV, respectively. The conduction band offsets are found to be ∼1.7eV for HfO2 films and ∼0.9eV for TiO2 films. The high-k HfO2∕TiO2 multilayers in p-Si∕SiO2∕(HfO2∕TiO2)∕Al2O3/aluminum memory capacitor show a large capacitance-voltage hysteresis memory window of ∼5V at gate voltage of ±5V, due to the charge storage in multilayer...

Charge storage characteristics of atomic layer deposited RuOx nanocrystals

The charge storage characteristics of atomic layer deposited RuOx nanocrystals embedded in high-k HfO2∕Al2O3 films in a metal/Al2O3∕RuOx∕HfO2∕SiO2∕n-Si structure have been investigated. The size and density of RuOx nanocrystals have been measured using transmission electron microscopy. The RuOx nanocrystals show a density of ∼1×1012∕cm2 and a diameter of 5–8nm. A large hysteresis memory window of ∼13.3V at a gate voltage of 9V has been observed for RuOx nanocrystal memory capacitors. A hysteresis memory window of 0.7V has also been observed under a small sweeping gate voltage of 1V. A promising memory window of RuOx nanocrystals has been observed as compared with those of pure HfO2 and Al2O3 charge trapping layers, due to charge storage in the RuOx metal nanocrystals. The RuOx nanocrystal memory capacitor has similar leakage current with the pure HfO2 and Al2O3 charge trapping layers. The RuOx memory capacitor has a large breakdown voltage of ∼13.8V.

Impact of metal nano layer thickness on tunneling oxide and memory performance of core-shell iridium-oxide nanocrystals

The impact of iridium-oxide (IrOx) nano layer thickness on the tunneling oxide and memory performance of IrOx metal nanocrystals in an n-Si/SiO2/Al2O3/IrOx/Al2O3/IrOx structure has been investigated. A thinner (1.5u2009nm) IrOx nano layer has shown better memory performance than that of a thicker one (2.5u2009nm). Core-shell IrOx nanocrystals with a small average diameter of 2.4u2009nm and a high density of ∼2u2009×u20091012/cm2 have been observed by scanning transmission electron microscopy. The IrOx nanocrystals are confirmed by x-ray photoelectron spectroscopy. A large memory window of 3.0u2009V at a sweeping gate voltage of ±5u2009V and 7.2u2009V at a sweeping gate voltage of ±u20098u2009V has been observed for the 1.5u2009nm-thick IrOx nano layer memory capacitors with a small equivalent oxide thickness of 8u2009nm. The electrons and holes are trapped in the core and annular regions of the IrOx nanocrystals, respectively, which is explained by Gibbs free energy. High electron and hole-trapping densities are found to be 1.5u2009×u20091013/cm2 and 2u2009×u20091013/...

Memory Characteristics of Atomic-Layer-Deposited High- κ HfAlO Nanocrystal Capacitors

The memory characteristics of atomic-layer-deposited high-K HfAlO nanocrystals in a p-Si/SiO 2 /CHfO 2 /Al 2 O 3 ]/Al 2 O 3 /platinum structure have been investigated. After the annealing treatment, the high-K HfAlO nanocrystals with a small diameter of 5 X 10 11 cm 2 have been observed by high-resolution transmission electron microscopy. A large hysteresis memory window of ∼ 10.4 V has been obtained. The high-K HfAlO nanocrystal memory capacitor with a small capacitance equivalent thickness of ∼ 8.5 ± 0.5 nm shows a small leakage current density of ∼ 22 μA cm 2 at a gate voltage of -16 V. A large memory window of ∼8 V has also been observed after 10 5 s of retention, due to the charge confinement in the high-K HfAlO multilayer nanocrystals.

Physical and Memory Characteristics of Atomic-Layer-Deposited High-κ Hafnium–Aluminum-Oxide Nanocrystal Capacitors with Iridium-Oxide Metal Gate

The physical and memory characteristics of high-κ hafnium–aluminum-oxide (HfAlO) nanocrystals in an n-Si/SiO2/HfO2/Al2O3/iridium-oxide (IrOx) structure have been investigated. The high-κ HfAlO nanocrystal in the SiO2/HfO2/Al2O3 layers is formed owing to the diffusion of Al2O3 and HfO2 films after high-temperature annealing at 900 °C. High-κ HfAlO nanocrystals with a small diameter of 5 nm and a high density of 1.7 ×1012 cm-2 have been confirmed by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Owing to the formation of high-κ HfAlO nanocrystals, a large hysteresis memory window of ΔV≈4.4 V at a sweeping gate voltage of ±10 V is observed compared with that of as-deposited memory capacitor. A hysteresis memory window of ΔV≈1.4 V with a small sweeping gate voltage of ±7 V is also observed. Good endurance of 104 cycles with a large memory window of ΔV≈3.6 V is obtained. A significant memory window of ΔV≈1.3 V is observed after a retention time of 5×104 s, owing to the charge confinement in the high-κ HfAlO nanocrystals.

Temperature-dependent physical and memory characteristics of atomic-layer-deposited RuO x metal nanocrystal capacitors

Physical and memory characteristics of the atomic-layer-deposited RuOx metal nanocrystal capacitors in an n-Si/SiO2/HfO2/ RuOx/Al2O3/Pt structure with different postdeposition annealing temperatures from 850-1000° have been investigated. The RuOx metal nanocrystals with an average diameter of 7nm and a highdensity of 0.7×1012/cm2 are observed by high-resolution transmission electron microscopy after a postdeposition annealing temperature at 1000°. The density of RuOx nanocrystal is decreased (slightly) by increasing the annealing temperatures, due to agglomeration of multiple nanocrystals. The RuO3 nanocrystals and Hf-silicate layer at the SiO2/HfO2 interface are confirmed by X-ray photoelectron spectroscopy. For postdeposition annealing temperature of 1000°, the memory capacitors with a small equivalent oxide thickness of ∼9 nm possess a large hysteresis memory window of >5V at a small sweeping gate voltage of ±5V. A promising memory window under a small sweeping gate voltage of ∼3 V is also observed due to charge trapping in the RuOx metal nanocrystals. The program/erase mechanism is modified Fowler-Nordheim (F-N) tunneling of the electrons and holes from Si substrate. The electrons and holes are trapped in the RuOx nanocrystals. Excellent program/erase endurance of 106 cycles and a large memory window of 4.3 V with a small charge loss of ∼23% at 85° are observed after 10 years of data retention time, due to the deep-level traps in the RuOx nanocrystals. The memory structure is very promising for future nanoscale nonvolatile memory applications.

Study of InGaN Multiple Quantum Dots by Metal Organic Chemical Vapor Deposition

We reports a study of InGaN multiple quantum dot layers. Using the in-situ SiNx treatment process, InGaN multiple quantum dot layers were successfully developed. The InGaN multiple quantum dot layers were constructed with SiNx dot mask layers, InGaN dot layers, and GaN cap layers on a 2-µm-thick GaN underlying layer on a sapphire substrate. Optical properties including room temperature photoluminescence (PL), temperature dependent PL, and low power power-dependent PL were examined and discussed. The structure was also analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) line scan.

High-/spl kappa/ HfO2/TiO2/HfO2 multilayer quantum well flash memory devices

High-kappa HfO₂/TiO₂/HfO₂ multilayer quantum well (MQW) charge storage devices with a large memory window of DeltaV_tap8.1 V, an excellent endurance and a good retention (~9% charge loss at 20degC) are reported. Both program and erase speeds of DeltaV_t>3 V@100 mus are achieved for memory transistors under channel hot carrier injections. Furthermore, quantum well memory capacitors with high-kappa Al₂O₃ as a blocking oxide and high work function metal gate show low leakage current density of ~2.4times10^-7 A/cm²@V_g=-5 V at 125degC and high program/erase speed of DeltaV_FB>2 V@10 mus with a low operation voltage of V_g<5 V.