• Applied Microscopy
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• v.27 no.3
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• pp.257-263
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• 1997

Microstructural characterizations of II-VI blue laser diodes which consist of quaternary $Zn_{1-x}Mg_xS_ySe_{l-y}$ cladding layer, ternary $ZnS_ySe_{l-y}$ guiding layer and $Zn_{0.8}Cd_{0.2}Se$ quantum well as active layer were carried out using the transmission electron microscope working at 300 kV. Even though the entire structure is pseudomorphic to GaAs substrate, the structure had contained numerous extended stacking faults and dislocations which had created at ZnSe/GaAs interfaces and then further grown to the top of the epilayers. These faults might be expected to cause the degradation and shortening the lifetime of laser devices.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.85.2-85.2
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• 2010

$Cu_2ZnSnSe_4$ (CZTSe) is one of candidate to alternate $Cu(In,Ga)Se_2$ as solar absorber material for solar cell. The expensive elements of In and Ga are replaced by Zn and Sn, respectively to lower the material cost. In this study we fabricated CZTSe thin film by selenization of single precursor layer consisted metallic constituent. Precursor compositions ratio were selected to have Cu-poor and Zn-rich content and prepared by RF magnetron sputtering. Thermal processing was applied to introduce selenium into as-deposited films at temperatures ranging from 350 to 500 for time up to 120 minutes. Single precursor films showed amorphous structure and consist of individual elements of Cu, Zn, and Sn. It was confirmed by XRD analysis that synthesis of CZTSe compound is occurred from lower temperature process, although concurrently additional phases such as binary cooper selenides are also existed. The quality of CZTSe crystal was improved as temperature increased. We also investigated the optical and electrical properties of as-selenized CZTSe as well.

• Journal of the Korean Vacuum Society
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• v.3 no.2
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• pp.212-219
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• 1994

Hot wall epitaxy법에 의하여 GaAs(100)aus 위에 ZnS-ZnSe 초격자를 성장하였다. ZnS-ZnSe 초격자의 주기는 x-선 회절 패턴에 의하여 확인되었고 이것은 변형을 고려하고 계산된 이론적인 패턴과 비교되었다. 경계면에 평행한 ZnS와 ZnSe의 변형의 비는 ZnSe에 대하여 ZnS의 두께기 증가할수록 감 소되었다. ZnS-ZnSe 초격자의 photoluminescence(PL)는 고에너지 영역의 예리한 스펙트럼과 저에너지 영역의 폭이 넓은 스펙트럼으로 구성되어있다. PL의 광자에너지는 Kronig-Penney 모델을 사용하여 계 산된 이론적인 에너지 값과 비교한 결과 type I의 초격자임을 알았다.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.33-41
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• 2003

The optical properties of $ZnS_ySe_{1-\chi-y}:Te_{\chi}(\chi<0.08,y~0.11)$ alloys grown by molecular beam epitaxy (MBE) have been investigated by photoluminescence (PL) and PL-excitation (PLE) spectroscopy. Good optical properties and high crystal quality were established with lattice match condition to GaAs substrate. At room temperature, emission in the visible spectrum region from blue to green was obtained by varying the Te content of the ZnSSe:Te alloy. The efficient blue and green emission were assigned to $Te_1 and Te_n(n\geq2)$cluster bound excitons, respectively. Bright green (535 nm) and blue (462 nm) light emitting diodes (LEDs) have been developed using ZnSSe:Te system as an active layer. The turn-on voltage of 2.1 V in current-voltage characteristics is very small compared to that of commercial InGaN-based LEDs (>3.4 V), indicating the formation of a good ohmic contact due to the optimized p-ZnSe/p-ZnTe multi-quantum well (MQW) superlattice electrode layers.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.458-464
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• 2006

The construction and the performance test of an ultra high vacuum (UHV) molecular beam epitaxy (MBE) system has been completed successfully. We have done domestic development and tried performance test for ultra high vacuum molecular beam epitaxy system. This system has reached pressure $2X10-^{10}$ Torr and the substrate has reached temperature $1,100^{\circ}C$. We have investigated into the characteristic of ZnSe/GaAs(001) by using scanning electron microscope (SEM), atomic force microscope (AFM), x-ray diffraction (XRD) and photolumi-nescence (PL).

• Current Photovoltaic Research
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• v.3 no.2
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• pp.54-60
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• 2015

ZnSnO thin films were deposited by atomic layer deposition (ALD) process using diethyl zinc ($Zn(C_2H_5)_2$) and tetrakis (dimethylamino) tin ($Sn(C_2H_6N)_4$) as metal precursors and water vapor as a reactant. ALD process has several advantages over other deposition methods such as precise thickness control, good conformality, and good uniformity for large area. The composition of ZnSnO thin films was controlled by varying the ratio of ZnO and $SnO_2$ ALD cycles. The ALD ZnSnO film was an amorphous state. The band gap of ZnSnO thin films increased as the Sn content increased. The CIGS solar cell using ZnSnO buffer layer showed about 18% energy conversion efficiency. With such a high efficiency with the ALD ZnSnO buffer and no light soaking effect, AlD ZnSnO buffer mighty be a good candidate to replace Zn(S,O) buffer in CIGSsolar cells.

• Current Photovoltaic Research
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• v.9 no.3
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• pp.96-105
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• 2021

Even though above 22% efficiencies have been reported in Cd-free Cu(In,Ga)Se₂ (CIGS) solar cell with Zn-containing buffers, the efficiencies with Zn-containing buffers, in general, are well below 20%. One of the reasons is Zn diffusion from the Zn-containing buffer layer to CIGS film during buffer growth. To avoid the degradation, it is necessary to prevent the diffusion of Zn atoms from Zn-containing buffer to CIGS film. For the purpose, we characterized an In₂Se₃ film as a possible diffusion barrier layer because In₂Se₃ has no Zn component. It was found that an In₂Se₃ layer grown at 300℃ was very effective in preventing Zn diffusion from a Zn-containing buffer. Also, the In₂Se₃ had a large potential barrier in the valence band at the In₂Se₃/CIGS interface. Therefore, In₂Se₃ passivation has the potential to achieve a super-high efficiency in CIGS solar cells that employ Cd-free ALD processed buffers containing Zn.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.378-378
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• 2010

The ZnSe epilayers were grown on the GaAs substrate by hot wall epitaxy. After the ZnSe epilayers treated in the vacuum-, Zn-, and Se-atmosphere, respectively, the defects of the epilayer were investigated by means of the low, temperature photoluminescence measurement. The dominant peaks at 2.7988 eV and 2.7937 eV obtained from the PL spectrum of the as-grown ZnSe epilayer were found to be consistent with the upper and the lower polariton peak of the exciton, $I_2$ ($D^{\circ}$, X), bounded to the neutral donor associated with the Se-vacancy. This donor-impurity binding energy was calculated to be 25.3 meV. The exciton peak, $I_l^d$, at 2.7812 eV was confirmed to be bound to the neutral acceptor corresponded with the Zn-vacancy.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.85-87
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• 2009

Despite the success of $Cu(In,Ga)Se_2$ (CIGS) based PV technology now emerging in several industrial initiatives, concerns about the cost of In and Ga are often expressed. It is believed that the cost of those elements will eventually limit the cost reduction of this technology. one candidate to replace CIGS is $Cu_2ZnSnSe_4$ (CZTSe), fabricated by co-evaporation technique. Effects of substrate temperature of $Cu_2ZnSnSe_4$ absorber layer on the performance of thin films solar cells were investigated. As substrate temperature increased, the grain size of $Cu_2ZnSnSe_4$ films increased presumably. At a optimal condition of substrate temperature is $320^{\circ}C$, the solar cell shows a conversion efficiency of 1.79% with $V_{OC}$ of 0.213V, JSC of $16.91mA/cm^2$ and FF of 49.7%.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.204-210
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• 2020

ZnO thin films are of considerable interest because they can be customized by various coating technologies to have high electrical conductivity and high visible light transmittance. Therefore, ZnO thin films can be applied to various optoelectronic device applications such as transparent conducting thin films, solar cells and displays. In this study, ZnO rod and thin films are fabricated using aqueous chemical bath deposition (CBD), which is a low-cost method at low temperatures, and environmentally friendly. To investigate the structural, electrical and optical properties of ZnO for the presence of citrate ion, which can significantly affect crystal form of ZnO, various amounts of the citrate ion are added to the aqueous CBD ZnO reaction bath. As a result, ZnO crystals show a nanorod form without citrate, but a continuous thin film when citrate is above a certain concentration. In addition, as the citrate concentration increases, the electrical conductivity of the ZnO thin films increases, and is almost unchanged above a certain citrate concentration. Cu(In,Ga)Se₂ (CIGS) solar cell substrates are used to evaluate whether aqueous CBD ZnO thin films can be applicable to real devices. The performance of aqueous CBD ZnO thin films shows performance similar to that of a sputter-deposited ZnO:Al thin film as top transparent electrodes of CIGS solar cells.