• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.171-171
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• 2010

GaN 기반 Light emitting diodes(LEDs)의 p-type doping layer는 일반적으로 hole을 발생시키는 acceptor로 Mg이 사용하되고 있다. 보통 Mg이 도핑된 p-type GaN은 >$1\;{\Omega}{\cdot}cm$의 저항이 존재하는데 그 이유는 Mg의 열적 이온화를 위한 activation 에너지가 높아서 상온에서 valence band의 hole concentration는 전체 억셉터 농도의 1%가 되지 않기 ��문이다. 본 논문에서는 높은 hole 농도를 얻기 위해서 metalorganic chemical-vapor deposition (MOCVD)를 장비를 사용하여 사파이어 기판의 misorientation-angle에 따른 p-type a-plane(11-20) GaN 특성을 분석하였다. misorientation-angle은 c축 방향으로 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 r-plane(1-102) 사파이어 기판 을 사용하였다. p-type 도핑물질로 bis-magnesium (Cp2Mg) 소스를 사용하였고 성장 과정중 발생하는 hydrogen passivation으로 인한 Mg-H complexes현상을 해결하기위해 conventional furnace annealing (CFA)와 rapid thermal annealing (RTA)를 이용하여 열처리 공정을 진행하였다. 열처리 공정은 Air와 N2 분위기에서 $650^{\circ}C$에서 $900^{\circ}C$ 사이의 다양한 온도에서 수행하였고 Hall 측정을 위해 Ni을 전극 물질로 사용하였다. 상온에서 Accent HL5500IU Hall system을 사용하여 hole concentration, mobility, specific resistance을 측정하였다. 열처리 공정 후 Hall측정 결과 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 각 샘플들은 온도, 시간, 분위기에 따라 hole concentration ($7.4{\times}10^{16}cm^{-3}{\sim}6{\times}10^{17}cm^{-3}$), mobility(${\mu}h=\;1.72\;cm^2/V-s\;{\sim}15.2\;cm^2/V-s$), specific resistance(4.971 ohm-cm ~8.924 ohm-cm) 가 변화됨을 확인 할 수 있었다. 또한 광학적 특성을 분석하기 위해 Photoluminescence (PL)을 측정하였다.

• Transactions on Electrical and Electronic Materials
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• 제4권6호
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• pp.9-12
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• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1002-1006
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• 2004

The studies on OLED(Organic Light-Emitting Diode) materials and structures have been researched in other to improve luminescence efficiency of OLED. Electrons and holes are injected into the devices, transported across the layer and recombine to form excitons, their profiles are sensitive to mobility velocity of electrons and holes. A suggested means of improving the efficiency of LEDs would be to balance the injection of electrons and holes into light emission layer of the device. In this paper, we demonstrate the difference of velocity between hole and electron by experiments, and compare with a data of simulation and experiment changing hole carrier transport layer thickness, so we get the optimal we improve luminescence efficiency. We improve understanding of the various luminescence efficiency through experiments and numerical analysis of luminescence efficiency in the hole carrier transport layer's thicknes.

• 세라미스트
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• 제21권1호
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• pp.98-111
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• 2018

The lead-based perovskite (CH3NH3PbI3) material has a high molar coefficient, high crystallinity at low temperature, and long range of balanced electron-hole transport length. In addition, PCE of perovskite solar cells (PSCs) has been dramatically improved by over 22% by amending the electronic quality of perovskite and by using state-of-the-art hole transporting materials (HTMs) such as tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) due to enhanced charge transport toward the electrode via properly aligned energy levels with respect to the perovskite. Replacing the spiro-OMeTAD with new HTMs with the desired properties of appropriate energy levels, high hole mobility in its pristine form, low cost, and easy processable materials is necessary for attaining highly efficient and stable PSCs, which are anticipated to be truly compatible for practical application. Furthermore, Recently Pb-free perovskite materials much attention as an alternative light-harvesting active layer material instead of lead based perovskite in photovoltaic cells. In this work, we demonstrate a Pb-free perovskite material for the light harvesting and emitter as optoelectronic devices.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.321-321
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• 2010

The PEDOT:PSS layer is usually used as hole transporting layer for the polymer bulk heterojunction solar cells. However, the interface between ITO and PEDOT:PSS is not stable and the chemical reaction between ITO and PEDOT can result in degraded device performance. We used the tungsten oxides as a hole transport layer by spin-coating. The $WO_3$ nanoparticles were well dispersed in ammonium hydroxide and deionized water and formed thin layer on the ITO anode. We found that $WO_3$ surface is more hydrophobic than the bare ITO or PEDOT:PSS-coated surfaces. The hydrophobic surfaces promote an ordered growth of P3HT films. A higher degree of P3HT ordering is expected to improve the hole mobility and the lifetime of the device using the tungsten oxide showed better stability compared to the device using the PEDOT:PSS.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.342-345
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• 2009

Bright light-emitting single crystal organic field-effect transistors (FETs) based on highly luminescent oligo(p-phenylenevinylene) (OPV) derivatives are demonstrated. Although OPV single crystal FETs show both p - and n - type FET operation, we found that an increase in the conjugation length of the OPV derivatives from three phenylene rings to five phenylene rings results in an improvement in the electron mobility by an order of magnitude, while retaining the high hole mobility with intense electroluminescence.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.282-283
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• 2006

The transport phenomena of arsenic (As) doped amorphous selenium(a-Se:As) thin film for digital X-ray conversion material has been reported. The effect of As addition on the carrier mobility and recombination lifetime in a-Se:As sample has been measured using the moving photo-carrier grating (MPG) technique. An Increase in hole mobility and recombination was observed when 0.3% arsenic, was added into a-Se sample, whereas electron mobility decrease with arsenic addition due to the defect density. The fabricated a-Se:03% As device exhibited the highest X-ray sensitivity.

• E2M - 전기 전자와 첨단 소재
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• 제10권6호
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• pp.581-588
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• 1997

The ionization energy and degree of ionization for Si and Ge with boron doping are calculated. The hole mobilities are then calculated as a function of doping concentration using the relaxation time approximation. When the screening effect is taken into account, the reduction of ionization energy results in the increase of degree of ionization. As a result, the calculated Si mobility becomes closer to the experimental data, whereas the calculated Ge mobility is almost independent of the screening effect. The inclusion of the broadening effect in the mobility calculation overestimates the ionized impurity scattering. As compared with the experiment, the screening effect is not avoidable to calculate Si and Ge mobilities, and the broadening effect must accompany with the hopping process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 학술대회 및 기술세미나 논문집 디스플레이 광소자
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• pp.85-88
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• 2006

The transport properties of amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. The effects of As addition on the carrier mobility and recombination lifetime in amorphous selenium (a-Se) films have been studied using the moving photocarrier grating (MPG) technique. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with the drift mobilities of holes and electrons obtained by time of flight (TOF) measurement.

• 대한전자공학회논문지SD
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• 제45권5호
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• pp.19-25
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• 2008

본 연구에서는 유기반도체인 펜타센과 소스-드레인 금속전극사이에 $C_{60}$을 홀주입층으로 적용한 유기박막트랜지스터를 제작하여 $C_{60}$을 삽입하지 않은 소자와의 전기적특성을 비교하였다. $C_{60}/Au$ 이중전극을 사용한 소자의 경우 Au단일전극을 사용한 소자와 비교하였을 때 전하이동도는 0.298 $cm^2/V{\cdot}s$에서 0.452 $cm^2/V{\cdot}s$ 문턱전압의 경우 -13.3V에서 -10.8V로 향상되었으며, contact resistance를 추출하여 비교하였을 경우 감소함을 확인할 수 있었다. 이러한 성능의 향상은 $C_{60}$을 Au와 pentacene 사이에 삽입하였을 경우 Au-pentacene 간의 원하지 않는 화학적 반응을 막아줌으로써 홀 주입장벽를 감소시켜 홀 주입이 향상되었기 때문이다. 또한 Al을 전극으로 적용한 OTFT도 제작하였다. 기존에 Al은 OTFT에 단일전극으로 사용하였을 경우 둘간의 높은 홀 주입장벽으로 인해 채널이 거의 형성되지 않았으나, $C_{60}/Al$ 이중전극을 사용한 소자의 경우 전하이동도와 전류점멸비은 0.165 $cm^2/V{\cdot}s$, $1.4{\times}10^4$ 으로써 Al를 단일전극으로 사용하는 소자의 전기적 특성에 비해 크게 향상되어진 소자를 제작할 수 있었다. 이는 $C_{60}$과 Al이 접합시에 interface dipole의 형성으로 Al의 vacuum energy level이 변화로 인한 Al의 work function이 증가되어 pentacene과 Al간의 hole injection barrier가 감소되었기 때문이다.