• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.275-286
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• 2005

The performance of the InGaN LED's in terms of the photon extraction efficiency has been analyzed by the Monte Carlo photon simulation method. Simulation results show that the sidewall slanting scheme, which works well for the AlInGaP or InGaN/SiC LED, plays a very minimal role in InGaN/sapphire LED's. In contrast to InGaN/SiC LED's, the lower refractive index sapphire substrate restricts the generated photons to enter the substrate, minimizing the chances for the photons to be deflected by the slanted sidewalls of the epitaxial semiconductor layers that are usually very thin. The limited photon transmission to the sapphire substrate also degrades the. photon extraction efficiency especially in the epitaxial-side down mount. One approach to exploit the photon extraction potential of the epitaxial-side down mount may be to texture the substrate-epitaxy interface. In this case, randomized photon deflection off the textured interface directly increases the number of the photons entering the sapphire substrate, from which they easily couple out of the chip and thereby improving the photon extraction efficiency drastically.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.87-92
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• 2007

A $CaAl_{12}O_{19}:Mn^{4+}$ red phosphor showed the highest emission intensity at a concentration of 0.02mole $Mn^{4+}$ and the high crystallinity and luminescent properties were obtained at $1600^{\circ}C$ firing temperature for 3hr. The synthesized phosphor showed a broad emission band at 658nm wavelength. Red light-emitting diodes(LEDs) were fabricated through the integration of on InGaN UV bare chip and a 1:3 ratio of $CaAl_{12}O_{19}:Mn^{4+}$ and epoxy resin in a single package. This coated LED can be applicable to make White LEDs under excitation energy of UV LED.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.3
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• pp.109-113
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• 2005

It has been reported that the failure phenomenon and variation of electrical characteristic due to the effect of electrostatic discharge(ESD) in silicon devices. But we had fess reports about the phenomenon due to the ESD in the compound semiconductors. So there are a lot of difficulty to the phenomenon analysis and to select the protection method of main circuits or the devices. It has not been reported that the relation between the ESD stress and GaN devices, which is remarkable to apply the operation in high temperature and high voltage due to the superior material characteristic. We studied that the characteristic variation of the AlGaN/GaN HEMT current, the leakage current, the transconductance(gm) and the failure phenomenon of device due to the ESD stress. We have applied the ESD stress by transmission line pulse(TLP) method, which is widely used in ESD stress experiments, and observed the variation of the electrical characteristic before and after applying the ESD stress. The on-current trended to increase after applying the ESD stress. The leakage current and transconductance were changed slightly. The failure point of device was mainly located in middle and edge sides of the gate, was considered the increase of temperature due to a leakage current. The GaN devices have poor thermal characteristic due to usage of the sapphire substrate, so it have been shown to easily fail at low voltage compared to the conventional GaAs devices.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.02a
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• pp.167-167
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• 1999

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.81-84
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• 2002

The effects of the isoelectronic AI-doping of GaN grown by metal organic chemical vapor deposition were investigated for the first time using scanning electron microscopy (SEM), Hall measurements, photoluminescence (PL), and time-resolved PL. When a certain amount of Al was incorporated into the GaN films, the room temperature photoluminescence intensity of the films was approximately two orders larger than that of the undoped GaN. More importantly, the electron mobility significantly increased from 130 for the undoped sample to $500\textrm{cm}^2/Vs$ for the sample grown at a TMAl flow rate of $10{\mu}mol/min$, while the unintentional background concentration only increased slightly relative to the TMAl flow. The incorporation of Al as an isoelectronic dopant into GaN was easy during MOCVD growth and significantly improved the optical and electrical properties of the film. This was believed to result from a reduction in the dislocation-related non-radiative recombination centers or certain other defects due to the isoelectronic Al-doping.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.4
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• pp.40-50
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• 1993

In this paper, MODFET devices with various gate length are simulated using the Monte-Carlo method. The number of superparticle is 5000 and the Poisson equation is solved to obtain field distribution. The structure of MODFET is n-AlGaAs/i-AlGaAs/iGaAs and doping concentration of n-AlGaAs layer is 1${\times}10^{17}/cm^{3}$ and the thickness is 500.angs., and the thickness of i-AlGaAs is 50$\AA$. The devices with gate length 0.2$\mu$m, 0.5$\mu$m, 1.0$\mu$m respctively are simulated and the current-voltage curves and transport characteristics of that devices are obtained. Occupancy of each subband and electron energy distribution and conduction energy band in channel have been analyzed to obtain transport characteristics, and particles transposed from source to drain have been analyzed to current-voltage curves. Current level is highest for the device of Lg=0.2$\mu$m and transconductance of this device is 310mS/mm.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.279-282
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• 2013

Recently, it has been interested much that AlN (Aluminum Nitride) crystals can be applied to UV LEDs and high power devices as like GaN and SiC crystals. The reports about commercial grade of AlN wafers in the world have been absent, however several results for growth of large size of AlN single crystals have been reported from abroad. In this report, the result of AlN single crystals of a diameter of about 8 mm grown are reported. Optical microscopic characterization was applied to observe the form of the crystals and the crystal quality was evaluated by FWHM measurement by DCXRD rocking curve analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.125-125
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• 2010

극성 [0001] 방향으로 성장된 질화물 기반의 LED (light emitting diode) 는 분극현상에 의해 발생하는 강한 내부 전기장의 영향을 받게 된다. 이러한 내부 전기장은 양자우물 내의 전자와 정공의 공간적 분리를 야기하고 quantum confined Stark effect (QCSE)에 의한 발광 파장의 적색 편이가 발생하며 양자효율의 저하를 가져오게 된다. 이러한 문제를 해결하기 위해 InGaN/GaN이나 AlGaN/GaN 양자 우물구조를 GaN의 m-plane (1$\bar{1}$00) 이나 a-plane (11$\bar{2}$0) 등 비극성면 위에 성장하려는 시도를 하고 있다. 그러나 비극성 면의 비등방성 (anisotropy) 으로 인하여 결정성이 높은 비극성 GaN을 성장하는 데에는 많은 어려움이 있다. GaN 층의 표면을 평탄화하고 결정성을 향상시키기 위해서 저온 GaN 또는 AlN 버퍼층을 성장하는 2단계 방법이나 고온 버퍼층을 이용하여 성장하는 연구들이 많이 진행되고 있다. 본 연구에서는 고온 GaN 버퍼층을 이용하여 기존의 2단계 성장과정을 단순화한 비극성 a-plane GaN을 r-plane 사파이어 기판위에 유기금속 화학증착법 (MOCVD)으로 성장하였다. 사파이어 기판위에 AlN 층을 형성하기 위한 nitridation 과정 후 1030 도에서 두께 45 ~ 800 nm의 고온 GaN 버퍼층을 성장하고 총 박막 두께가 2.7 ~ 3 um 가 되도록 a-plane GaN을 성장하여 표면 양상의 변화와 결정성을 확인하였다. 또한 a-plane GaN 박막 성장 시에 성장 압력을 100 ~ 300 torr 로 조절하며 박막 성장의 변화 양상을 관찰하였다. 고온 GaN 버퍼층 성장 두께가 감소함에 따라 결정성은 증가하였으나 표면의 삼각형 형태의 pit 밀도가 증가함을 확인하였다. 또한 성장 압력이 감소함에 따라 표면 pit은 감소하였으나 결정성도 감소하는 것을 확인하였다. 성장 압력과 버퍼층 성장 두께를 조절하여 표면에 삼각형 형태의 pit이 존재하지 않는 RMS roughness 0.99 nm, 관통전위밀도 $1.78\;{\times}\;10^{10}/cm^2$, XRD 반가폭이 [0001], [1$\bar{1}$00] 방향으로 각 798, 1909 arcsec 인 a-plane GaN을 성장하였다. 이 연구를 통해 고온 GaN 버퍼 성장방법을 이용하여 간소화된 공정으로 LED 소자 제작에 사용할 수 있는 결정성 높은 a-plane GaN을 성장할 수 있는 가능성을 확인하였다.

• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.28-33
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• 1994

The laser-assisted chemical vapor deposition (LCVD) is described, by which the growth of single-phase GaN epitaxy is achieved at lower temperatures. Trimethylgallium (TMG) and ammonia are used as source gases to deposit the epitaxial films of GaN under the irradiation of ArF excimer laser (193 nm). The as-grown deposits are obtained on c-face sapphire surface near 700$^{\circ}$C, which is substantially reduced, relative to the temperatures in conventional thermolytic processes. To overcome the lattice mismatch between c-face sapphire and GaN ad-layer, aluminum nitride(AlN) is predeposited as buffer layer prior to the deposition of GaN. The gas phase interaction is monitored by means of quadrupole mass analyzer (QMA). The stoichiometric deposition is ascertained by X-ray photoelectron spectroscopy (XPS). The GaN deposits thus obtained are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and van der Pauw method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.8-14
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• 2011

The optimal geometry of the gate field plate in AlGaN/GaN-on-Si HEMT has been proposed using two-dimensional device simulation to achieve a high breakdown voltage for a given gate-to-drain distance. It was found that the breakdown voltage was drastically enhanced due to the reduced electric field at the gate corner when a gate field plate was employed. The electric field distribution at the gate corner and the field plate edge was investigated as functions of field plate length and insulator thickness. According to the simulation results, the electric field at the gate corner can be successfully reduced even with the field plate length of 1 ${\mu}m$. On the other hand, when the field plate length is too long, the distance between field plate and drain electrode is reduced below a critical level, which eventually lowers the breakdown voltage. The highest breakdown voltage was achieved with the field plate length of 1 ${\mu}m$. According to the simulation results varying the $SiN_x$ film thickness for the fixed field plate length of 1 ${\mu}m$, the optimum thickness range of the $SiN_x$ film was 200 - 300 nm where the electric field strength at the field plate edge counterbalances that of the gate corner.