• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.312-312
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• 2013

GaN based light emitting diodes (LEDs) are important devices that are being used extensively in our daily life. For example, these devices are used in traffic light lamps, outdoor full-color displays and backlight of liquid crystal display panels. To realize high-brightness GaN based LEDs for solid-state lighting applications, the development of p-type ohmic electrodes that have low contact resistivity, high optical transmittance and high refractive index is essential. To this effect, indiumtin oxide (ITO) have been investigated for LEDs. Among the transparent electrodes for LEDs, ITO has been one of the promising electrodes on p-GaN layers owing to its excellent properties in optical, electrical conductivity, substrate adhesion, hardness, and chemical inertness. Sputtering and e-beam evaporation techniques are the most commonly used deposition methods. Commonly, ITO films on p-GaN by sputtering have better transmittance and resistivity than ITO films on p-GaN by e-bam evaporation. However, ITO films on p-GaN by sputtering have higher specific contact resistance, it has been demonstrated that this is due to possible plasma damage on the p-GaN in the sputtering process. In this paper, we have investigated the advanced sputtering using plasma damage-free p-electrode. Prepared the ITO films on the GaN based LEDs by e-beam evaporation, normal sputtering and advanced sputtering. The ITO films on GaN based LEDs by sputtering showed better transmittance and sheets resistance than ITO films on the GaN based LEDs by e-beam evaporation. Finally, fabricated of GaN based LEDs by using advanced sputtering. And compared the electrical properties (measurement by using C-TLM) and structural properties (HR-TEM and FE-SEM) of ITO films on GaN based LEDs produced by e-beam evaporation, normal sputtering and advanced sputtering. As a result, It is expected to form plasma damage free-electrode, and better light output power and break down voltage than LEDs by e-beam evaporation and normal sputter.

• 한국진공학회지
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• 제15권3호
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• pp.301-307
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• 2006

P-modulation doping된 In(Ga)As/InGaAsP 양자점에서의 decay time 특성을 undoped 양자점 시료와의 비교를 통해 살펴보았다. 10 K 에서의 photoluminescence (PL) 세기는 doping 된 양자점이 doping되지 않은 양자점에 비해 약 10배 정도 약하게 나왔다. 또한 Time resolved PL (TR-PL) 실험을 통해 얻은 양자점 시료의 기저상태 PL peak 에서의 decay time은 doping된 양자점이 doping 되지 않은 양자점에 비해 매우 짧게 나왔다. 이러한 PL 세기와 decay time 특성을 통해서 본 연구에서 측정한 doping 된 양자점의 경우에는 doping에 의해 결함이 증가하게 되고, 그로 인해 운반자의 비발광 경로가 증가하게 되어 doping 된 양자점의 경우에 decay time이 짧게 나타나는 것으로 분석하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.25-28
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• 2001

In this paper, we have investigated the effects of gas flow rate, rf power, process pressure and Ar addition on reactive ion etching of InP, InGaAs and InAlAs using Sic14 and Cl$_2$ gases. The etch rates were measured by using a surface profiler. The etched profiles, sidewall roughness, and surface morphology were observed by scanning electron microscopy and by atomic force microscopy. The selective etching of InGaAs to InP and InAlAs was studied by varying the etching parameters. It was found that Cl$_2$ gas is more efficient for the selective etching of InGaAs to InAlAs than SiCl$_4$ gas. The etch selectivity of InGaAs to InAlAs is strongly dependent on the rf power and the process pressure.

• 마이크로전자및패키징학회지
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• 제24권4호
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• pp.59-63
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• 2017

n-type GaN 반도체는 광전극으로서 우수한 성질을 가지고 있지만, 표면에서 일어나는 산소반응으로 인한 광부식으로 신뢰성이 저하되는 큰 단점이 있다. 이를 근본적으로 억제하기 위하여 표면에서 수소 발생 반응이 일어나는 p-type GaN를 광전극으로 사용함으로써 광부식을 피하고자 하는 연구가 진행되고 있다. 하지만 p-type GaN은 비저항이 높고 정공 이동도가 낮기 때문에 효율이 낮다는 단점을 가지고 있다. 본 연구에서는 이러한 문제를 p-type GaN의 activation 공정을 통해 개선하고자 한다. 전극으로 사용될 p-type GaN을 $N_2$ 분위기의 $500^{\circ}C$에서 1 분 동안 annealing을 하였다. Hall effect 측정을 통하여 전기적 특성을 확인하였으며, potentiostat (PARSTAT4000) 측정을 통하여 광전기화학적 (photoelectrochemical, PEC) 특성을 분석하였다. 그 결과 annealing 공정을 통하여 광전류밀도가 1.5배 이상 향상되었으며, 3시간 동안 안정적인 광전류 값을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.322.2-322.2
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• 2014

Lighting emitting diodes of n-ZnO/MQW/p-GaN structure are fabricated and investigated. To realize this LED structure, n-ZnO/MQW/p-GaN are grown by MOCVD. At several bias voltages, blue-green light is emitted from the ZnO mesa edge. However, the emission is restricted near the mesa edge. It is seen that the hole current does not spread well. It is because conductivity of p-GaN is extremely small. The break down voltage of the device is small compared to conventional InGaN/GaN LEDs. It is seen that ZnO columnar grain boundaries act as leakage current paths and non-radiative recombination center.

• 센서학회지
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• 제17권5호
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• pp.346-349
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• 2008

A metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) is proposed as an effective UV sensing device for integration with a GaN n-channel MISFET on auto-doped p-type GaN grown on a silicon substrate. Due to the high hole barrier of the metal-p-GaN contact, the dark current density of the fabricated MSM PD was less than $3\;nA/cm^2$ at a bias of up to 5 V. Meanwhile, the UV/visible rejection ratio was 400 and the cutoff wavelength of the spectral responsivity was 365 nm. However, the UV/visible ratio was limited by the sub-bandgap response, which was attributed to defectrelated deep traps in the p-GaN layer of the MSM PD. In conclusion, an MSM PD has a high process compatibility with the n-channel GaN Schottky barrier MISFET fabrication process and epitaxy on a silicon substrate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.50-50
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• 2008

ZnO has been extensively studied for optoelectronic applications such as blue and ultraviolet (UV) light emitters and detectors, because it has a wide band gap (3.37 eV) anda large exciton binding energy of ~60 meV over GaN (~26 meV). However, the fabrication of the light emitting devices using ZnO homojunctions is suffered from the lack of reproducibility of the p-type ZnO with high hall concentration and mobility. Thus, the ZnO-based p-n heterojunction light emitting diode (LED) using p-Si and p-GaN would be expected to exhibit stable device performance compared to the homojunction LED. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducibleavailability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices with low defect density. However, the electroluminescence (EL) of the device using n-ZnO/p-GaN heterojunctions shows the blue and greenish emissions, which are attributed to the emission from the p-GaN and deep-level defects. In this work, the n-ZnO:Ga/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated at different growth temperatures and carrier concentrations in the n-type region. The effects of the growth temperature and carrier concentration on the electrical and emission properties were investigated. The I-V and the EL results showed that the device performance of the heterostructure LEDs, such as turn-on voltage and true ultraviolet emission, developed through the insertion of a thin intrinsic layer between n-ZnO:Ga and p-GaN:Mg. This observation was attributed to a lowering of the energy barriers for the supply of electrons and holes into intrinsic ZnO, and recombination in the intrinsic ZnO with the absence of deep level emission.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.66-69
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• 1997

The p-GaN fins doped with the impurity of Zn were grown on n-GaN films to prevent the defects from the lattice mismatch with sapphire substrates by HVPE. For growth of the high quality n-GaN, the optimized conditions were at first deduced from the results of various HCI gas flow rates and growth temperatures. On the basis of these conditions, p-GaN films were grown and investigated of the characteristics. The FWHM of the double crystal rocking curve of n-GaN was decreased and the hexagonal phases on the surface of GaN films were tend to be vivid with the inoement of HCI gas flow rates. Finally the n-type GaN films with FWHM of 648arcsec were obtained at 10cc/min of HCI gas. As the GaN films were grown with the above conditions, Zn was introduced in the form of vapor as a dopant for p-GaN films. But when Zn vaporized at 77$0^{\circ}C$ was doped to the films, the crystallites of Zn were distributed uniformly on the surface of the GaN film due to the over-doped.

• The Journal of Korean Physical Therapy
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• 제14권2호
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• pp.234-249
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• 2002

This study was performed, using c-fos and Substance P, to investigate the effect of GaAlAs laser on acute pain model induced by wound in lumbar region's spinal level. The test group was divided into control and experimental group. Control group is shamed group(c-fos and substance P expression after non-irradiation by a GaAlAs laser), The experimental group was divided into two subgroups: one is experimental group I (c-fos expression after irradiation by a GaAlAs laser), and the other is experimental group II (substance P expression after irradiation by a GaAlAs laser). The results of this study were as following: 1. The numbers of c-fos immunoreactive neuron in spinal cord was increased markedly 1 day after wound, and decreased gradually from 1 day to 2 days in wound with GaAlAs laser irradiation. 2. The changes of the average percentages of substance P immunoreactive neurons in spinal cord was increased markedly 1 day after wound, and decreased gradually from 1 day to 2 days in wound with GaAlAs laser irradiation. Therefore, decreasing the changes of c-fos and substance P expression after irradiation by a GaAlAs laser indicates and GaAlAs laser have effect on pain control.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.405-408
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• 1998

Due to the large conduction band discontinuity between emitter base, OmGaAs HBT has an advantge to enable the hot electrons to inject into the base. In this paper, InAlGaAs/InGaAs HBT with the various emitter junction gradings and the modified collectors are simulated and analyzed by HMC(hybrid monte carlo) simulator in order to find a optimal structure for the shortest transit time. A minium base transit time (.tau.$_{b}$ ) of 0.21 ps was obtained for HBT with the grading layer, which is parabolically graded from x=1.0 to x=0.5. The minimum collector transit time (.tau.$_{c}$ ) of 0.31ps was found when the collector was modified by inserting p$^{[-10]}$ and p$^{+}$ layers. Thus HBT in combination with the emitter grading and the modified collector layer showed the cut-off frequency (f$_{T}$) of 183GHz.z.z.