• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.59-60
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• 2005

The characteristics of GaN epitaxial layers grown on silicon (111) substrates by metalorganic vapor phase epitaxy have been investigated. The only control of AIN thickness was found to decrease the stress sufficiently for avoiding crack formation in an overgrown thick ($2.6{\mu}m$) CaN layer. X-ray diffraction measurementsare used to determine the effect of AIN thickness on the strain in the subsequent GaN layers. The 437arcsec linewidth on the (002) x-ray rocking curve also attest the high crystalline quality of GaN on Si (111).

• 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.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.769-774
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• 2003

In this paper, we report on the DC characteristics of the AlGaN/GaN HFETs using physical models on piezoelectric and thermal effects. Employing the models was found to be essential for a realistic prediction of the DC current-voltage characteristics of the AlGaN/GaN HFETs. Though use of the implementation of the physical models, peak drain current, transconductance, pinch-off voltage, and most importantly, the negative slope in the current were accurately predicted. The importance of the heat sink effect was demonstrated by the comparison of the DC characteristics of AlGaN/GaN HFETs fabricated from different substrates including sapphire, Si and SiC. Highest peak current was achieved from the device with SiC by an effective suppression of heat sink effect.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.2
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• pp.54-57
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• 2005

Photoreflectance (PR) has been measured to investigate the characterization of the Si$_{3}$N$_{4}$Al$_{0.21}$ Ga$_{0.79}$As/GaAs and Al$_{0.21}$Ga$_{0.79}$As/GaAs heterostructures. In the PR spectrum, the caplayer thickness was 170 nm and Si$_{3}$N$_{4}$ was utilized as the capping material. The C peak is confirmed as the carbon defect with residual impurity originating from the growth process. After annealing, in the presence of the Si$_{2}$N$_{4}$ cap layer, band gap energy was low shifted. This result indicates that the Si$_{3}$N$_{4}$ cap layer controlled evaporation of the As atom.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.945-949
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• 2005

We have grown GaN layers with in-situ SiN mask by metal organic chemical vapor deposition (MOCVD) and study the physical properties of the GaN layer. We have also fabricate PN junction light emitting diode (LED) to investigate the effect of the SiN mask on its optical property By inserting a SiN mask, (102) the full width at half maximum (FWHM) decreased from 480 arcsec to 409 arcsec and threading dislocation (TD) density decreased from $3.21{\times}10^9\;cm^{-2}$ to $9.7{\times}10^8\;cm^{-2}$. The output power of the LED with a SiN mask increased from 198 mcd to 392 mcd at 20 mA. We have thus shown that the SiN mask improved significantly the physical and optical properties of the GaN layer.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.16-21
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• 2015

In this study, the effects of forming gas post metallization annealing (PMA) on recessed AlGaN/GaN-on-Si MOSHFET were investigated. The device employed an ICPCVD $SiO_2$ film as a gate oxide layer on which a Ni/Au gate was evaporated. The PMA process was carried out at $350^{\circ}C$ in forming gas ambient. It was found that the device instability was improved with significant reduction in interface trap density by forming gas PMA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.1
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• pp.1-6
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• 2017

Tungsten carbide (WC) has been suggested as a new buffer layer for the GaN-on-Si technology. We have investigated and optimized the sputtering condition of WC layer on the Si-substrate. We confirmed the suppression of the Si melt-back phenomenon. In addition, surface energy of WC/Si layer was measured to confirm the possibility as a buffer layer for GaN growth. We found that the surface energy(${\gamma}=82.46mJ/cm^2$) of WC layer is very similar to that of sapphire substrate(${\gamma}=82.71mJ/cm^2$). We grow GaN layer on the WC buffer by using gas-source MBE, and confirm that it is available to grow a single crystalline GaN layer.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.65-66
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• 2006

AIGaN/GaN 고전자 이동도 트랜지스터 (High Electron Mobility Transistors, HEMTs)는 와이드 밴드-갭과 높은 항복 전계 및 우수한 채널 특성으로 인해 마이크로파 응용분야와 전력용 반도체에서 각광받고 있다. 최근, 전력 응용분야에서 요구되는 높은 항복 전압과 출력, 우수한 주파수 특성을 획득하기 인해 이중 게이트 AIGaN/GaN HEHTs에 관한 연구가 발표되고 있다. 본 논문에서는 AIGaN/GaN HEMTs에 이중 게이트를 적용하여, 두 개의 게이트와 드레인, 소스의 누설 전류를 각각 측정하여 이중 게이트 AIGaN/GaN HEMTS의 누설 전류 메커니즘을 분석하였다. 또한 제안된 소자의 $SiO_2$ 패시베이션 전 후의 누설 전류 특성을 비교하였다. $SiO_2 $ 패시베이션되지 않은 소자의 누설 전류는 드레인, 소스와 추가 게이트로부터 주 게이트로 흐른 반면, 패시베이션 된 소자 누설 전류는 드레인으로부터 주 게이트 방향의 누설 전류만 존재하였다. $SiO_2$ 패시베이션 된 소자의 누설 전류는 (87.31 nA ) 패시베이션 되지 않은 소자의 누설 전류 ( $8.54{\mu}A$ )에 비해 의게 감소하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.71-73
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• 1995

In this work, we synthsized GaN powders by the direct reactions of Ga with NH$_3$at the temperature range of 950∼1150$^{\circ}C$ and we growth the GaN thin films on Si and sapphire substrates using the synthesized GaN powders by the vapor phase epitaxy method. The synthesized powder had hexagonal crystal structures with lattice constants of a$\sub$0/=3.1895${\AA}$, c$\sub$0/=5.18394${\AA}$. The reaction rates of GaN were increased with both reaction time and temperature, however it did not depends on the flow rates of NH$_3$. The island type GaN crystals were grown on (0001) sapphire substrates and fast lateral growth of GaN on (111) Si substrate than sapphire was observed in our experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.187-188
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• 2005

The characteristics of GaN epitaxial layers grown on silicon (111) substrates by metalorganic vapor phase epitaxy have been investigated. The only control of AlN thickness was found to decrease the stress sufficiently for avoiding crack formation in an overgrown thick ($2.6{\mu}m$) GaN layer. X-ray diffraction and photoluminescence measurements are used to determine the effect of AlN thickness on the strain in the subsequent GaN layers. Strong band edge photoluminescence of GaN on Si(111) was observed with a full width at half maximum of the bound exciton line as low as 17meV at 13K.