• Journal of the Korean Vacuum Society
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• v.2 no.4
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• pp.424-432
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• 1993

AlGaAs/InGaAs/GaAs pseudomorphic structures have been grown by atmosheric pressure-MOCVD . The Al incorporation efficiency is constant but slightly exceeds the Ga incorporation during the growth of AlGaAs layers at $650^{\circ}C$ . Meanwhile , the In incorporation efficiency is constant but slightly less than the Ga incorporation in InGAAs layers. InGaAs/GaAs QWs were grown and their optical properties were characterized . $\delta$-doped Al0.24Ga0.76As/In0.16 Ga0.84As p-HEMT structures were successfully grown by MOCVD and their transport properties were characterized by Hall effect and SdH measurements. SdH Measurements at 3.7K show clear magnetoresistance oscillations and plateaus in the quantum Hall effect confirming the existence of a two-dimensional electron gas(2DEG) and a parallel conduction through the GaAs buffer layer. The fabricated $1.5\mu\textrm{m}$gatelength p-HEMTs having p-type GaAs in the buffer layer show a high transconductance of 200 mS/mm and a good pinch-off characteristics.

• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.296-300
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• 2014

The synthesis of pure and rare-earth doped gallium oxide (${\beta}-Ga_2O_3$) nanoparticles is reported. The synthesized nanoparticles are characterized with XRD, TEM, and PL analyses. Strong blue emission is observed from un-doped gallium oxide nanoparticles, while nanoparticles doped with $Eu^{3+}$ and $Tb^{3+}$ give strong red and green emissions, respectively. When doped with $Eu^{3+}$ and $Tb^{3+}$ together, gallium oxide nanoparticles emit white light. The CIE coordinate of the emitted light was found to be (0.33, 0.33), which is well within the white light region.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.135-140
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• 2011

By investigating photoluminescence (PL) spectra (20 K) of undoped and Be-doped p-type GaSb/GaAs epilayers, the origin has been analyzed by the change due to doping density. We have observed that the PL peak shifts to higher energy and the full-width half-maximum (FWHM) decreases with increasing the doping density below ${\sim}10^{17}cm^{-3}$, contrasted to shift to low energy and increasing FWHM above the density of ${\sim}10^{17}cm^{-3}$. From the variation of the integrated PL intensities of three peaks dissolved by Gaussian fit, it has been analyzed that, as the density increases, the $Be[Be_{Ga}]$ acceptor level (0.794 eV) reduces, whereas the intrinsic defect of $A[Ga_{Sb}]$ (0.778 eV) enhances together with a new $Be^*$ level (0.787 eV) locating between A and Be. We have discussed that it is due to coexistence of the Be acceptor level (${\Delta}E=16meV$) and the complex level (${\Delta}E=23meV$), $Be^*[Ga_{Sb}-Be_{Ga}]$combined by Be and A, in Be-doped p-GaSb, and that the level density of $Be[Be_{Ga}]$ may be reduced above ${\sim}10^{17}cm^{-3}$.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.94-101
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• 2023

Zinc oxide(ZnO) is a semiconductor material with a bandgap of 3.37 eV and an exciton binding energy of 60 meV for various applications. Recently ZnO has been proven to enhance its electrical properties for utilization as an alternative for transparent conducting oxide (TCO) materials. In this study, cation(Al, Ga)-anion(F) single and double doped ZnO thin films were grown by atomic layer deposition (ALD) to enhance the electrical properties. The structural and optical properties of doped ZnO thin films were analyzed, and doping effects were confirmed to electrical characteristics. In single doped ZnO, it was observed that the carrier concentration was increased after doping, acting as a donor to ZnO. Among the single doping elements, F doped ZnO(FZO) showed the highest mobility and conductivity due to the passivation effect of oxygen vacancies. In the case of double doping, higher electrical characteristics were observed compared to single doping. Among the samples, Al-F doped ZnO(AFZO) exhibited the lowest resistance value. This results can be attributed to an increase in delocalized electron states and a decrease in lattice distortion resulting from the differences in ionic radius. The partial density of states(PDOS) was also analyzed and observed to be consistent with the experimental results.

• Korean Journal of Materials Research
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• v.13 no.11
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• pp.717-720
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• 2003

Heavily $p^{ ＋}$-typed ($10^{20}$ $cm^{-3}$ ) GaAs epilayers have been grown on high-index GaAs substrates with various crystallographic orientations from (100) to (111)A by a low-pressure metalorganic chemical vapor deposition. Carbon (C) tetrabromide (CBr$_4$) was used as a C source. At moderate growth temperatures and high V/III ratios, the hole concentration of C-doped GaAs epilayers shows the crystallographic orientation dependence. The bonding strength of As sites on a growing surface plays an important role in the C incorporation into the high-index GaAs substrates.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.23-23
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• 2003

GaN-related semiconductors are of great technological importance for the fabrication of optoelectronic devices, such as blue and ultra violet light emitting diodes (LEDs), laser diodes, and photo-detectors. One of the most important applications of GaN-based LEDs is solid-state lighting, which could replace incandescent bulbs and ultimately fluorescent lamps. For solid-state lighting applications, the achievement of high extraction efficiency in LED structures is essential. For flip-chip LEDs (FCLEDS), the formation of low resistance and high reflective p-GaN contact is crucial. So far, a wide variety of different methods have been employed to improve the ohmic properties of p-type contacts to GaN. For example, surface treatments using different chemical solutions have been successfully used to produce high-quality ohmic contacts, Metallization schemes, such as Ta/Ti contacts to p-GaN, were also investigated. For these contacts, the removal of hydrogen atoms from the Mg atoms doped n the GaN was argued to be responsible for low contact resistances.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.112-116
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• 2001

고상반응법에 의한 제조한 ZnGa$_2$O$_4$형광체에 Li 및 Tm 원소를 도핑함에 따른 발광특성을 조사하였다. 254nm 여기 하에서, 환원 처리된 ZnGa$_2$O$_4$형광체는 245nm에서 흡수피크와 380nm에서 발광피크를 나타내며, 이는 스피넬 구조에서 Ga$^{3+}$ 이온의 $^4$T$_2$$\longrightarrow$$^4$A$_2$천이에 기인한다. ZnGa$_2$O$_4$형광체에 있어서 Li 및 Tm을 도핑했을 경우가 도핑하지 않은 시료에 비해 발광강도 및 색순도가 개선되었으며, Li 및 Tm을 각각 0.1 mol, 0.01 mol 첨가했을 때 가장 우수한 발광강도 및 색순도 특성을 보였다.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.107-112
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• 2011

This paper is for improving the RF frequency performance of a fabricated 100nm ${\Gamma}$-gate MHEMT, scaling down vertically for the epitaxy-structure layers of the device. Hydrodynamic simulation parameters are calibrated for the fabricated MHEMT with the modulation-doped $In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}$As heterostructure grown on the GaAs substrate. With these calibrated parameters, simulations for the vertically-scaled epitaxial layers of the device are performed and analyzed for DC/RF characteristics, including the quantization effect due to the thickness reduction of InGaAs channel layer. A newly designed epitaxy-structure device shows higher extrinsic transconductance, $g_m$ of 1.556 S/mm, and higher frequency performance, $f_T$ of 222.5 GHz and $f_{max}$ of 849.6 GHz.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.83-91
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• 1994

We have constructed a vertical gradient freeze (VGF) grower for GaAs single crystals 2 inch in diameter and have grown semi-insulating GaAs co-doped with Cr and In. For the co-doped crystal, the segregation coefficients of the dopants remain unchanged when compared to those doped with only Cr or In. The concentration of Cr and in atoms range from about $2{\Times}10_{16} to 3{imes}10^{17} cm^{-3}$ and $2{\Times}10^{19} to 3{\Times}10^{20} cm^{-3}$ at the seed to the tail part of the grown crystal, respectively. The averaged dislocation etch pit density is found to be less than $8000 cm^{-2}$ throughout the ingot. It is also found that there is some evidence of lattice hardening for the crystal in which the dislocation density is decreased to less than $1000 cm^{-2}$ as In concentration increases. The resistivity increases abruptly from $10^{-2}$ up to $10^8$ Ohm-cm, while the carrier concentration decreases from $10^{16}$ to $10^8 cm^{-3}$ along the growth direction of the GaAs crystal. Semi-insulating properties can be obtained above a critical concentration of Cr of about $6{\Times}10{^16} cm^{-3}$ in the crystal. The main deep levels existing in the GaAs: Cr,In sample are two electron traps at $E_C-0.81eV, E_C-0.35eV$, and two hole traps at $E_V+0.89eV, E_V+0.65eV$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.242-247
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• 1998

In this study, we have synthesized $ZnGa_2O_4$:Mn,X powder doped with Mn, MnO, $MnF_2$ and $MnCl_2$, low voltage green emitting phosphor, in vacuum atmosphere. From PL spectra, the intensity of the emission peak, the brightness with coactivator show that $ZnGa_2O_4$:Mn,Cl > $ZnGa_2O_4$:Mn,F > $ZnGa_2O_4$:Mn,O > $ZnGa_2O_4$:Mn. These improvement of the brightness are caused by the increase of the concentration of $Mn^{2+}$ ion. In case of $ZnGa_2O_4$:Mn,Cl and ZnGa$_2$O$_4$:Mn,F, the brightness is enhanced much more, which is owed to the decrease of defect of host material. For $ZnGa_2O_4$:Mn,Cl phosphor fabricated with optimized condition, the decay time becomes short from 30 ms of the $ZnGa_2O_4$:Mn and $ZnGa_2O_4$:Mn,O to 6 ms and the brightness of CL at 1 kV, 1 mA is 60 cd/$m^2$.