• JSTS:Journal of Semiconductor Technology and Science
• /
• v.9 no.3
• /
• pp.166-173
• /
• 2009

The reliability of hafnium oxide gate dielectrics incorporating lanthanum (La) is investigated. nMOSFETs with metal/La-doped high-k dielectric stack show lower $V_{th}$ and $I_{gate}$, which is attributed to the dipole formation at the high-k/$SiO_2$ interface. The reliability results well correlate with the dipole model. Due to lower trapping efficiency, the La-doping of the high-k gate stacks can provide better PBTI immunity, as well as lower charge trapping compared to the control HfSiO stacks. While the devices with La show better immunity to positive bias temperature instability (PBTI) under normal operating conditions, the threshold voltage shift (${\Delta}V_{th}$) at high field PBTI is significant. The results of a transconductance shift (${\Delta}G_m$) that traps are easily generated during high field stress because the La weakens atomic bonding in the interface layer.

• Journal of the Korean Ceramic Society
• /
• v.56 no.4
• /
• pp.374-386
• /
• 2019

A process for nitrogen doping of TiO₂ ceramics was developed, whereby polycrystalline titania particles were prepared at 450-1000℃ with variation of the firing schedule under N₂ atmosphere. The effect of nitrogen doping on the polycrystallites was investigated by X-ray diffraction (XRD) and Raman analysis. The microstructure of the TiO₂ ceramics changed with variation of the firing temperature and the firing atmosphere (N₂ or O₂). The microstructural changes in the nitrogen-doped TiO₂ ceramics were closely related to changes in the Raman spectra. Within the evaluated temperature range, the nitrogen-doped titania ceramics comprised anatase and/or rutile phases, similar to those of titania ceramics fired in air. Infiltration of nitrogen gas into the titania ceramics was analyzed by Raman spectroscopy and XRD analysis, showing a considerable change in the profiles of the N₂-doped TiO₂ ceramics compared with those of the TiO₂ ceramics fired under O₂ atmosphere. The nitrogen doping in the anatase phase may produce active sites for photocatalysis in the visible and ultraviolet regions.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.387-392
• /
• 2018

Static characteristics of SiC (silicon carbide) lateral p-i-n diodes implemented on semi-insulating substrate without an epitaxial layer are inVestigated. On-axis SiC HPSI (high purity semi-insulating) and VDSI (Vanadium doped semi-insulating) substrates are used to fabricate the lateral p-i-n diode. The space between anode and cathode ($L_{AC}$) is Varied from 5 to $20{\mu}m$ to inVestigate the effect of intrinsic-region length on static characteristics. Maximum breakdown Voltages of HPSI and VDSI are 1117 and 841 V at $L_{AC}=20{\mu}m$, respectiVely. Due to the doped Vanadium ions in VDSI substrate, diffusion length of carriers in the VDSI substrate is less than that of the HPSI substrate. A forward Voltage drop of the diode implemented on VDSI substrate is 12 V at the forward current of $1{\mu}A$, which is higher than 2.5 V of the diode implemented on HPSI substrate.

• Carbon letters
• /
• v.22
• /
• pp.60-69
• /
• 2017

Nitrogen-doped carbon nanosheets with a developed porous structure were prepared from polyurethane foams by hydrothermal carbonization following $ZnCl_2$ chemical activation. Scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, solid state $^{13}C$ nuclear magnetic resonance (NMR) spectra and X-ray photoelectron spectroscopy were used to characterize the nitrogen-doped carbon nanosheet structure and composition. The removal of Cr(VI) by the N-doped carbon nanosheets was investigated. The results showed that the maximum removal capacity for chromium of 188 mg/g was found at pH=2.0 with PHC-Z-3. pH had an important effect on Cr(VI) removal and the optimal pH was 2.0. Moreover, amino groups and carboxyl groups in the nitrogen-doped carbon nanosheet played important roles in Cr(VI) removal, and promoted the reduction of Cr(VI) to Cr(III).

• Advances in nano research
• /
• v.3 no.2
• /
• pp.55-66
• /
• 2015

Crystalline $Ce^{3+}$ co-doped $LaPO_4$:RE ($RE=Dy^{3+}$, $Tb^{3+}$, $Eu^{3+}$, $Sm^{3+}$) and mix doped rare earth ions of $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ were prepared by the polyol method at $150^{\circ}C$. Strongly enhance luminescence intensity is obtained with the co-doping of $Ce^{3+}$ with $LaPO_4$:$Dy^{3+}$ and $LaPO_4$:$Tb^{3+}$ due to charge transfer (CT) occurring from $Ce^{3+}$ to $Dy^{3+}$ and $Ce^{3+}$ to $Tb^{3+}$, where as there is no significant changes in luminescence intensity of $Ce^{3+}$ co-doped $Eu^{3+}$ and $Sm^{3+}$ doped $LaPO_4$ samples. The luminescence color can be tuned from green to white by varying the excitation wavelength for the mix ions $Ce^{3+}$, $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ doped with $LaPO_4$.

• Proceedings of the IEEK Conference
• /
• 2001.06b
• /
• pp.217-220
• /
• 2001

CaN(gallium nitride) MODFET(modulation doped field effect transistor) large signal model was studied using Modified Materka-Kacprzak large signal MODFET model. using the Dambrine's method［3, at 45MHz-40㎓, Measured S-parameter and DC characteristics. based on measuring results, small signal parameter extraction was conducted. by the cold FET［4］method, measured parasitic elements were de-embedding. Extracted small signal parameters were modeled using modified Materka model, a sort of fitting function reproduce measuring results. to confirm conducted large signal modeling, modeled GaN MODFET's DC, S-parameter and Power characteristics were compared to measured results, respectively. by results were represented comparatively agreement, this paper showed that modified Materka model was useful in the GaN MODFET large signal modeling.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.6 no.2
• /
• pp.79-86
• /
• 2006

N-polar, Ga-polar, and non-polar GaN was grown by MBE and MOVPE using various substrates and influence of polarity has been investigated. The GaN growth by MOVPE is along cplane (0001), c-plane (0001), and a-plane (11-20) direction on c-plane (0001), a-plane (11-20) and r-plane (1-102) sapphire substrate respectively. The polarity of the film has a strong influence on the morphology and the optical properties of PA-MBE grown As-doped GaN layers. Strong blue emission from As-doped GaN was observed only in the case of N-polarity (000-1) layers, which was attributed to the highest concentration of Ga dangling bonds for this polarity of a GaN surface.

• Journal of the Korean Vacuum Society
• /
• v.15 no.6
• /
• pp.624-629
• /
• 2006

The energy transfer process between GaN and Nd ions as well as Mg codoping effect were investigated in Nd-implanted GaN films. Photoluminescence (PL) and PL excitation spectroscopies were performed on $^4F_{3/2}{\rightarrow}^4I_{9/2}$ Nd ionic level transition. At least three below bandgap traps were identified in the energy transfer process. The number of one particular trap, which is assigned to be an isoelectronic Nd trap, is increased with the Mg-codoping. The emission efficiency with above gap excitation, which emulates the electrical excitation, is further increased in GaN:Mg,Nd.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.283-283
• /
• 2011

The n-doping effect by doping metal carbonate into an electron-injecting organic layer can improve the device performance by the balanced carrier injection because an electron ohmic contact between cathode and an electron-transporting layer, for example, a high current density, a high efficiency, a high luminance, and a low power consumption. In the study, first, we investigated an electron-ohmic property of electron-only device, which has a ITO/$Rb_2CO_3$-doped $C_{60}$/Al structure. Second, we examined the I-V-L characteristics of all-ohmic OLEDs, which are glass/ITO/$MoO_x$-doped NPB (25%, 5 nm)/NPB (63 nm)/$Alq_3$ (32 nm)/$Rb_2CO_3$-doped $C_{60}$(y%, 10 nm)/Al. The $MoO_x$doped NPB and $Rb_2CO_3$-doped fullerene layer were used as the hole-ohmic contact and electron-ohmic contact layer in all-ohmic OLEDs, respectively, Third, the electronic structure of the $Rb_2CO_3$-doped $C_{60}$-doped interfaces were investigated by analyzing photoemission properties, such as x-ray photoemission spectroscopy (XPS), Ultraviolet Photoemission spectroscopy (UPS), and Near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, as a doping concentration at the interfaces of $Rb_2CO_3$-doped fullerene are changed. Finally, the correlation between the device performance in all ohmic devices and the interfacial property of the $Rb_2CO_3$-doped $C_{60}$ thin film was discussed with an energy band diagram.

• Journal of the Korean Ceramic Society
• /
• v.37 no.5
• /
• pp.432-437
• /
• 2000

Thermoelectric properties of p-type SiGe alloys prepared by a RF inductive furnace were investigated. Non-doped Si80Ge20 alloys were fabricated by control of the quantity of volatile Ge. The carrier of p-type SiGe alloy was controlled by B-doping. B doped p-type SiGe alloys were synthesized by melting the mixture of Ge and Si containing B. The effects of sintering/annealing conditions and compaction pressure on thermoelectric properties (electrical conductivity and Seebeck coefficient) were investigated. For nondoped SiGe alloys, electrical conductivity increased with increasing temperatures and Seebeck coefficient was measured negative showing a typical n-type semiconductivity. On the other hand, B-doped SiGe alloys exhibited positive Seebeck coefficient and their electrical conductivity decreased with increasing temperatures. Thermoelectric properties were more sensitive to compaction pressure than annealing time. The highest power factor obtained in this work was 8.89${\times}$10-6J/cm$.$K2$.$s for 1 at% B-doped SiGe alloy.