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  • Title/Summary/Keyword: Ga doped

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Effects of Strontium Gallate Additions on Sintering Behavior and Electrical Conductivity of Ce0.8Gd0.2O2-δ Ceramics (Strontium Gallate의 첨가에 따른 Ce0.8Gd0.2O2-δ 세라믹스의 소결거동과 전기전도도 특성)

  • Park Jin-Hee;Choi Kwang-Hoon;Ryu Bong-Ki;Lee Joo-Sin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.2
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    • pp.145-152
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    • 2006
  • The densification behavior and electrical conductivity of Ce0.8Gd0.2O1.9 ceramics were investigated with the strontium gallate concentration ranging from 0 to 5mol%. Both the sintered density and grain size were found to increase rapidly up to 0.5mol% Sr2Ga2O5, and then to decrease with further addition. Dense Ce0.8Gd0.2O1.9 ceramics with 97% of the theoretical density could be obtained for 0.5mol% Sr2Ga2O5-added specimen sintered at 1250C for 5 h, whereas pure Ce0.8Gd0.2O1.9 ceramics needed to be sintered at 1550C in order to obtain an equivalent theoretical density, Electrical conductivity was measured as a function of dopant content, over the temperature range of 350600C in air. Total conductivity of 0.5mol% Sr2Ga2O5-added specimen showed the maximum conductivity of 2.37×102Ω1cm1 at 500C, The addition of strontium gallate was found to promote the sintering properties and electrical conductivities of Gd2O3-doped CeO2.

Luminescence Characteristics of Ba2+ Co-Doped Sr2SiO4:Eu Yellow Phosphor for Light Emitting Diodes (LED용 Ba2+ Co-Doped Sr2SiO4:Eu 황색 형광체의 발광특성)

  • Choi, Kyoung-Jae;Park, Joung-Kyu;Kim, Kyung-Nam;Kim, Chang-Hae;Kim, Ho-Kun
    • Journal of the Korean Ceramic Society
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    • v.43 no.3 s.286
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    • pp.169-172
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    • 2006
  • We have synthesized a Eu2+activated(Sr,Ba)2SiO4 yellow phosphor and investigated the development of blue LEDs by combining the phosphor with a InGaN blue LED chip (λem=405 nm). The InGaN-based (Sr,Ba)2SiO4:Eu LED lamp shows two bands at 405 nm and 550 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the (Sr,Ba)2SiO4:Eu phosphor. The 550 nm emission band is ascribed to a radiative recombination of Eu2+ impurity ions in the (Sr,Ba)2SiO4 host matrix. In the preparation of UV Yellow LED Lamp with (Sr,Ba)2SiO4:Eu yellow phosphor, the highest luminescence efficiency was obtained at the epoxy-to-yellow phosphor ratio of 1:0.45. At this ratio, the CIE chromaticity was x=0.4097 and y=0.5488.

A Study on Electroreflectance in Si-Doped Al0.33Ga0.67As (Si이 첨가된 Al0.33Ga0.67As에서의 Electroreflectance에 관한 연구)

  • 김근형;김동렬;김종수;김인수;배인호;한병국
    • Electrical & Electronic Materials
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    • v.10 no.7
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    • pp.692-699
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    • 1997
  • The silicon doped Al0.33G a0.67As were grown by molecular beam epitaxy. The electroreflectance(ER) spectra of Schottky barrier Au/n-Al/suu x/G a1x As have been measured at various modulation voltage( Vac ) and dc bias voltage( Vbias). From the observed Franz-Keldysh oscillations(FKO) peak, the band gap energy of the AlxG a1x As is 1.91 eV which corresponds to an Al composition of 33%. The internal electric field( Ei)of this sample is 2.96×105 V/cm. As the modulation voltage( Vac ) is changed, the line shape of ER signal does not change but its amplitude varies linearly. The amplitude as a function of modulation voltage has saturated at 0.8 V. The internal electric field has decreased from 6.47×105 V/cm to 2.00×105 V/cm as the dc bias voltage( Vbias) increases from -3.5 V to +0.8 V. The values of built-in voltage( Vbi ) and carrier concentration(N) determined from the plot of Vbias from the plot of Vbias versus Ei2 are 0.855 V and 3.83×1017 c m3 , respectively.ively.y.y.y.

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CdSe Quantum Dot based Transparent Light-emitting Device using Silver Nanowire/Ga-doped ZnO Composite Electrode (AgNWs/Ga-doped ZnO 복합전극 적용 CdSe양자점 기반 투명발광소자)

  • Park, Jehong;Kim, Hyojun;Kang, Hyeonwoo;Kim, Jongsu;Jeong, Yongseok
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.4
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    • pp.6-10
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    • 2020
  • The silver nanowires (AgNWs) were synthesized by the conventional polyol process, which revealed 25 ㎛ and 30 nm of average length and diameter, respectively. The synthesized AgNWs were applied to the CdSe/CdZnS quantum dot (QD) based transparent light-emitting device (LED). The device using a randomly networked AgNWs electrode had some problems such as the high threshold voltage (for operating the device) due to the random pores from the networked AgNWs. As a method of improvement, a composite electrode was formed by overlaying the ZnO:Ga on the AgNWs network. The device used the composite electrode revealed a low threshold voltage (4.4 Vth) and high current density compared to the AgNWs only electrode device. The brightness and current density of the device using composite electrode were 55.57 cd/㎡ and 41.54 mA/㎠ at the operating voltage of 12.8 V, respectively, while the brightness and current density of the device using (single) AgNWs only were 1.71 cd/㎡ and 2.05 mA/㎠ at the same operating voltage. The transmittance of the device revealed 65 % in a range of visible light. Besides the reliability of the devices was confirmed that the device using the composite electrode revealed 2 times longer lifetime than that of the AgNWs only electrode device.

Ridge Formation by Dry-Etching of Pd and AlGaN/GaN Superlattice for the Fabrication of GaN Blue Laser Diodes

  • Kim, Jae-Gwan;Lee, Dong-Min;Park, Min-Ju;Hwang, Seong-Ju;Lee, Seong-Nam;Gwak, Jun-Seop;Lee, Ji-Myeon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.391-392
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    • 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 CHF3 and Cl2 -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 Cl2 (90%)/Ar (10%) and Cl2 (50%)/CHF3 (50%) plasma chemistry, respectively. While when the Cl2/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the Cl2/CHF3 plasma shows decreased etch rate, compared with that of Cl2/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 Cl2/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 (Cl2/CHF3) and SLs (Cl2/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.

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Structural dependences of the extinction in an 1.55 1.55μm InGaAsP/InGaAsP multiple-quantum-well electro-absorption modulator (1.55 1.55μm InGaAsP/InGaAsP MQW 광흡수 변조기에서 구조변수가 소광특성에 미치는 영향)

  • 민영선;심종인;어영선
    • Korean Journal of Optics and Photonics
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    • v.12 no.1
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    • pp.40-47
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    • 2001
  • The structural dependence of the performance of an 1.55 1.55μm InGaAsPIInGaAsP MQW electro-absorption modulator for highspeed digital fiber communication was systematically investigated. The effects of n-doped SCH region length tn as well as the general structure parameters including quantum well number Nw, well-thickness tw, detuning wavelength Δλ, and device length L were thoroughly analyzed. Thereby, a high-pelfoIDlance electro-absorption modulator with device length L of 100μm was successfully designed. The designed structure showed excellent characteristics that have residual loss less than -1.5 dB, operational voltage from 0 V to -2V, and extinction ratios of -2.92 dB at Vα=-1 V and -10 dB at Vα=-2V.X>=-2V.

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Photoconductivity in Mg-doped p-type GaN by MBE

  • ;;;;;Yuldashev
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.120-120
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    • 1999
  • III-nitride계 물질들은 blue와 UV 영역의 LED, LD와 같은 광소자뿐만 아니라 HBT, FET와 같은 전자소자로도 널리 응용되고 있다. 이와 같은 물질을 이용한 소자를 제작할 수 있는 낮은 저항의 ohmic contact은 필수적이다. Al이나 Ti와 같은 물질을 기초로 한 n-GaN의 경우는 이미 많은 연구결과가 발표되어 전기적 광학적 소자를 동작하는데 충분히 낮은 ohmic contact저항( )을 었다. 그러나 p-GaN의 ohmic contact은 아직까지 많은 문제점을 내포하고 있다. 그 중의 하나는 높은 doping 농도( )의 p-GaN 박막을 성장하기가 어렵다는 것이며, 또 하나는 낮은 접촉 비저항을 얻기 위해선 7.5eV이상의 큰 재가 function을 지닌 금속을 선택해야 한다. 그러나 5.5eV 이상의 재가 function을 갖는 금속은 존재하지 않는다. 위와 같은 문제점들은 p-GaN의 접촉 비저항이 이상의 높은 값을 갖게 만들고 있으며, 이에 대한 해경방안으로는 고온의 열처리를 통하여 p-GaN와 금속 사이에서 화학적 반응을 일으킴으로써 표면 근처에서 캐리어농도를 증가시키고, 캐리어 수송의 형태가 tunneling 형태로 일어날 수 있도록 하는 tunneling current mechanism을 이용하는 것이다. 이로 인해 결국 낮은 접촉 비저항을 얻을 수 있게되며, 일반적으로 p-GaN에서는 Nidl 좋은 물질로 알려져 있다. 그러나 Ni은 500C이상의 열처리에서 쉽게 산화되는 특성 때문에 높은 캐리어를 얻는데 어려운 문제점이 있다. 이에 본 연구에서는 MBE로 성장된 p-GaN박막을 Mg의 activation을 더욱 증가시키기 위해 N2 분위기에서 15분간 900C에서 annealing을 하였으며, ohmic 접촉을 위한 금속으로 높은 재가 function과 좋은 adhesion 그리고 낮은 자체저항을 가지고 있는 Ni/Au를 ohmic metal로 하여 contact한 후에 900C에서 10초간 rapid thermal annealing (RTA)처리를 했다. 성장된 박막의 광학적 성질은 PL로써 측정하였으며, photoconductivity 실험을 통해 impurity의 life time을 분석하였고, persistent photoconductivity를 통해 dark current를 측정하였다. 또한 contact resistance를 계산하기 위해 circular-TLM method을 이용하여 I-V 특성을 조사하였다.

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High Performance GaN-Based Light-Emitting Diodes by Increased Hole Concentration Via Graphene Oxide Sheets

  • Jeong, Hyun;Jeong, Seung Yol;Jeong, Hyun Joon;Park, Doo Jae;Kim, Yong Hwan;Kim, HyoJung;Lee, Geon-Woong;Jeong, Mun Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.244.1-244.1
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    • 2013
  • The p-type GaN which act as a hole injection layer in GaN-based LEDs has fundamental problems. The first one arises from the difficulty in growing a highly doped p-GaN (with a carrier concentration exceeding ~1018 cm3). And the second one is the absence of appropriate metals or conducting oxides having a work function that is larger than that of p-type GaN (7.5 eV). Moreover, the LED efficiency is decreases gradually as the injection current increases (the so-called 'efficiency droop' phenomenon). The efficiency droop phenomenon in InGaN quantum wells (QWs) has been a large obstacle that has hindered high-efficiency operation at high current density. In this study, we introduce the new approaches to improve the light-output power of LEDs by using graphene oxide sheets. Graphene oxide has many functional groups such as the oxygen epoxide, the hydroxyl, and the carboxyl groups. Due to nature of such functional groups, graphene oxide possess a lot of hole carriers. If graphene oxide combine with LED top surface, graphene oxide may supply hole carriers to p-type GaN layer which has relatively low free carrier concentration less than electron concentration in n-type GaN layer. To prove the enhancement factor of graphene oxide coated LEDs, we have investigated electrical and optical properties by using ultra-violet photo-excited spectroscopy, confocal scanning electroluminescence microscopy.

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In0.64Al0.36Sb층의 성장온도 및 도핑에 따른 광학적 특성

  • O, Jae-Won;Kim, Hui-Yeon;Ryu, Mi-Lee;Im, Ju-Yeong;Sin, Sang-Hun;Kim, Su-Yeon;Song, Jin-Dong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.160-160
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    • 2010
  • 테라헤르츠 소스로 저온 InGaAs를 대체하기 위해 저온에서 성장한 In0.64Al0.36Sb의 성장 온도에 따른 광학적 photoluminescence (PL)과 time-resolved PL (TRPL) 측정을 이용하여 분석하였다. 또한 Be 도핑 농도에 따른 p형 In0.64Al0.36Sb의 PL과 TRPL 특성을 undoped In0.64Al0.36Sb와 Si-doped In0.64Al0.36Sb 결과와 비교 분석하였다. 본 연구에 사용한 시료는 분자선 엑피탁시 (molecular beam epitaxy)법으로 GaAs 기판 위에 In0.64Al0.36Sb을 다양한 성장온도에서 3.7μm두께 성장하였다. In0.64Al0.36Sb의 성장온도는 400C 에서 460C까지 변화시키며 성장하였으며, Si과 Be 도핑한 In0.64Al0.36Sb 시료는 약 420C에서 성장하였다. 모든 시료의 PL 피크는 ~1450 nm 근처에서 나타나며 단파장 영역에 shoulder 피크가 나타났다. 그러나 가장 낮은 온도 400C에서 성장한 시료는 1400 nm에서 1600 nm에 걸쳐 매우 넓은 피크가 측정되었다. PL 세기는 450C 에서 성장한 시료가 가장 강하게 나타났으며, 435C에서 성장한 시료의 PL 세기가 가장 약하게 나타났다. 방출파장에 따른 PL 소멸곡선을 측정하였으며 double exponential function을 이용하여 운반자 수명시간을 계산하였다. 운반자 수명시간은 빠른 소멸성분 τ1과 느린 소멸성분 τ2가 존재하고 빠른 성분 τ1의 PL 진폭이 약 80%로 느린 성분 τ2보다 우세하게 나타났다. 각 PL 피크에서의 운반자 수명시간 τ1은 ~1 ns로 성장온도에 따른 변화는 관찰되지 않았다. 또한 방출파장이 1400 nm에서 1480 nm까지 PL 피크 근처에서 운반자 수명시간은 거의 일정하게 나타났다. Be-doped 시료의 PL 피크는 1236 nm에서 나타나며, Si-doped 시료는 1288 nm, undoped 시료는 1430 nm에서 PL 피크가 측정되었다. PL 피크에서 PL 소멸곡선은 Be-doped 시료가 가장 빨리 감소하였으며, Si-doped 시료가 가장 길게 나타났다. 이러한 결과로부터 In0.64Al0.36Sb의 광학적 특성은 성장 온도, dopant type, 도핑 농도에 따라 변화하는 것을 확인하였다.

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Electrical and structure properties of W ohmic contacts to InGaN (W/InGaN Ohmic 접촉의 전기적 구조적 특성연구)

  • Han-Ki Kim;Tae-Yeon Seong
    • Proceedings of the Materials Research Society of Korea Conference
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    • 1999.11a
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    • pp.76-76
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    • 1999
  • Low resistance ohmic contacts to the Si-doped InGaN(~×1019 ㎤) were obtained using the W metallization schemes. Specific contact resistance decreased with increasing annealing temperature. The lowest resistance is obtained after a nitrogen ambient annealing at 950C for 90s, which results in a specific contact resistance of 2.75×108cm2. Interfacial reactions and surface are analyzed using x-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The X-ray diffraction results show that the reactions between the W film and the InGaN produce a β-W2N phase at the interface. TEM results also show that the β-W2N has a rough interface, which increase contact area. It shows that the morphology of the contacts is stable up to a temperature as high as 950C. Possible mechanisms are proposed to describe the annealing temperature dependence of the specific contact resistance.

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