• 한국전기전자재료학회논문지
• /
• 제17권7호
• /
• pp.764-769
• /
• 2004

In order to reduce operating voltage of the GaN based blue-violet laser diodes, the effect of highly Mg doped GaN layer, which was grown below ohmic contact metals, on contact resistivity as well as operating voltage has been investigated. The addition of the highly Mg doped GaN layer greatly reduced contact resistivity of Pd/Pt/Au ohmic contacts from $5.2 \times {10}^-2 \Omegaㆍ$\textrm{cm}^2$ to 7.5 \times {10}^-4 \Omegaㆍ$\textrm{cm}^2$$. In addition, it also decreased device voltage at 20 mA by more than 3 V. Temperature- dependent sheet resistivity of the highly Mg doped GaN layer suggested that the reduction of the contact resistivity could be attributed to predominant current flow at the interface between the Pd/Pt/Au contacts and p-GaN through a deep level defect band, rather than the valence band.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
• /
• pp.48-49
• /
• 2001

GaN는 wurzite structure를 갖는 wide bandgap III-V족 반도체로서, 청색 반도체 laser diode (LD), light emitting diode (LED)등으로 응용되는 물질이다. InGaN quantum well은 GaN계의 청색 LD, LED 구조에서 활성층으로 사용되기 때문에 이에 대한 광학적 연구가 활발하다. InGaN는 GaN위에 성장하면 strain에 의해 piezoelectric 효과가 크게 나타나는 것으로 알려져 있다. 이러한 piezoelectric potential에 의해 외부에서 voltage가 가해지지 않은 상황에서도 InGaN quantum well내의 electron, hole의 wave function이 비대칭 potential의 영향을 받게된다. (중략)

• Applied Science and Convergence Technology
• /
• 제26권4호
• /
• pp.79-85
• /
• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• Journal of the Optical Society of Korea
• /
• 제14권4호
• /
• pp.415-419
• /
• 2010

A phosphor-conversion white light source is demonstrated using an InGaN-based blue laser diode (LD) and a yellow-emitting phosphor excited by the blue LD. The photometric and colorimetric properties of this blue-LD-based white light source are characterized. When injection current of the LD is 100 mA, luminous flux and luminous efficiency of the white light are found to be over 5 lm and 10 lm/W, respectively. When injection current is >90 mA, luminance is estimated to be larger than 10 Mcd/$cm^2$. In addition, color characteristics of the white light such as chromaticity coordinates, a correlated color temperature, and a color rendering index are found to be quite stable as current and temperature of the LD varies. The demonstrated LD-based white light source is expected to be used in high-brightness illumination applications with good color stability.

• Journal of the Optical Society of Korea
• /
• 제13권3호
• /
• pp.386-391
• /
• 2009

PSPICE circuit parameters of the blue laser diodes grown on wurtzite AlGaInN multiple quantum well structures were extracted directly from the three level rate equations. The relevant optical gain parameters were separately calculated from the self-consistent multiband Hamiltonian. The resulting equivalent circuit model for a blue laser diode was schematically presented, and its modulation characteristics, including the pulse response and the frequency response, have been demonstrated by using a conventional PSPICE.

• 한국마이크로전자및패키징학회:학술대회논문집
• /
• 한국마이크로전자및패키징학회 2004년도 추계 기술심포지움 초록집
• /
• pp.30-30
• /
• 2004

• E2M - 전기 전자와 첨단 소재
• /
• 제15권6호
• /
• pp.31-34
• /
• 2002

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
• /
• pp.20-20
• /
• 2003

We developed 30 ㎽-AlInGaN based violet laser diodes. The fabrication procedures of the laser diodes are described as follows. Firstly, GaN layers having very low defect density were grown on sapphire substrates by lateral epitaxial overgrowth method. The typical dislocation density was about 1-3$\times$10$^{6}$ /$\textrm{cm}^2$ at the wing region. Secondly, AlInGaN laser structures were grown on LEO-GaN/sapphire substrates by MOCVD. UV activation method, instead of conventional annealing, was conducted to achieve good p-type conduction. Thirdly, ridge stripe laser structures were fabricated. The cavity mirrors were formed by cleaving method. Three pairs of SiO$_2$ and TiO$_2$ layers were deposited on the rear facet for mirror coating. Lastly, laser diode chips were mounted on AlN submount wafers by epi-down bonding method. The lifetime of the laser diodes was over 10,000 hrs at room temperature under automatic power controlled condition. We expect the performance of the LDs to be improved by the optimization of the growth and fabrication process. The detailed characteristics and important issues of the laser diodes will be discussed at the conference.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.391-392
• /
• 2012

In these days, the desire for the precise and tiny displays in mobile application has been increased strongly. Currently, laser displays ranging from large-size laser TV to mobile projectors, are commercially available or due to appear on the market [1]. In order to achieve a mobile projectors, the semiconductor laser diodes should be used as a laser source due to their size and weight. In this presentation, the continuous etch characteristics of Pd and AlGaN/GaN superlattice for the fabrication of blue laser diodes were investigated by using inductively coupled $CHF_3$ and $Cl_2$ -based plasma. The GaN laser diode samples were grown on the sapphire (0001) substrate using a metal organic chemical vapor deposition system. A Si-doped GaN layer was grown on the substrate, followed by growth of LD structures, including the active layers of InGaN/GaN quantum well and barriers layer, as shown in other literature [2], and the palladium was used as a p-type ohmic contact metal. The etch rate of AlGaN/GaN superlattice (2.5/2.5 nm for 100 periods) and n-GaN by using $Cl_2$ (90%)/Ar (10%) and $Cl_2$ (50%)/$CHF_3$ (50%) plasma chemistry, respectively. While when the $Cl_2$/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the $Cl_2/CHF_3$ plasma shows decreased etch rate, compared with that of $Cl_2$/Ar plasma, especially for AlGaN/GaN superlattice. Furthermore, it was also found that the Pd which is deposited on top of the superlattice couldn't be etched with $Cl_2$/Ar plasma. It was indicating that the etching step should be separated into 2 steps for the Pd etching and the superlattice etching, respectively. The etched surface of stacked Pd/superlattice as a result of 2-step etching process including Pd etching ($Cl_2/CHF_3$) and SLs ($Cl_2$/Ar) etching, respectively. EDX results shows that the etched surface is a GaN waveguide free from the Al, indicating the SLs were fully removed by etching. Furthermore, the optical and electrical properties will be also investigated in this presentation. In summary, Pd/AlGaN/GaN SLs were successfully etched exploiting noble 2-step etching processes.

• 한국진공학회지
• /
• 제18권4호
• /
• pp.266-271
• /
• 2009

Migration Enhanced Molecular Beam Epitaxy를 통해 성장한 GaAs 기반 1300 nm 파장대역 InAs 양자점 레이저 다이오드의 발진 특성을 연구하였다. 펄스 및 상온 연속 동작에서 전류 주입 및 동작 온도 변화에 따른 L-I 특성과 발진 스펙트럼 측정을 통해 바닥준위(1302 nm)에서 여기준위(1206 nm)로의 발진 파장의 전환을 관찰하였으며 이는 양자점 바닥준위 이득의 포화로 이해된다. 상온 펄스 동작시 문턱전류 밀도는 92 A/$cm^2$, 발진 파장은 1311 nm이며, 상온 연속 동작시 문턱전류 밀도는 247 A/$cm^2$, 발진 파장은 1320 nm이다.