Point-Defect Study of CuAlSe2(112) Layers Post-Annealed in Various Ambient

홍광준,윤창주,김혜숙,방진주,문종대,하종호,정태수 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.5I

High quality CuAlSe2(112)/GaAs(100) heteroepitaxial layers were grown by using the hot wall epitaxy method. The optical absorption measurement showed the temperature dependence of the energy band gap on the CuAlSe2 layer to be Eg(T) = 2.8382 eV . (8.68 × 10.4 eV/K)T2/(155 + T). After the as-grown CuAlSe2 layer was annealed in Cu, Se, and Al atmospheres, the origin of point defects in the CuAlSe2 layer were investigated by using photoluminescence (PL) at 10 K. Point defects originating from VCu, VSe, Cuint, and Seint were obtained from the PL measurements and were classified as a donor or acceptor types. These PL results also led us to confirm that the CuAlSe2 layer had obviously converted into an n-type after the Cu atmosphere treatment. Finally, we found that the Al in the CuAlSe2 layer did not form native defects because the Al existed in the form of stable bonds in the CuAlSe2 layer.or.

CBD 방법에 의한 CdS 박막의 성장과 광전도 특성

홍광준,이상열,유상하,서상석,문종대,신영진,정태수,신현길,김택성,송정훈,유기수 ( K . J . Hong,S . Y . Lee,S . H . You,S . S . Suh,J . D . Moon,Y . J . Shin,T . S . Jeoung,H . K . Shin,T . S . Kim,J . H . Song,K . S . Rheu ) 한국센서학회 1993 센서학회지 Vol.2 No.1

Polycrystalline CdS thin films were grown on ceramic substrate using a chemical bath deposition method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdS polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdS samples annealed in N₂ gas at 5500 it was found hexagonal structure whose lattice constants a_o and c_o were 4.1364 Å and 6.7129 Å, respectively. Its grain size was about 0.35 ㎛. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33K and 150K and by polar optical scattering at temperature range of 150K and 293K. We measured also spectral response, sensitivity (γ), maximum allowable power dissipation and response time on these samples.

The temperature-dependent behavior of the photocurrent spectra of CdIn2S4 films

홍광준,Sukjin Yun,Jangbok Kim 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.4

CdIn2S4 (110) films were grown on semi-insulating GaAs (100) by a hot wall epitaxy method. Using photocurrent (PC) measurements, the PC spectra in the temperature range of 30 to 10 K appeared as three peaks in the short wavelength region. It was found that three peaks, A-, B-, and C-excitons, correspond to the intrinsic transition from the valence band states of Γ4(z), Γ5(x), and Γ5(y) to the exciton below the conduction band state of Γ1(s), respectively. A 0.122 eV crystal field splitting and the 0.017 eV spin orbit splitting were obtained. Thus, the temperature dependence of the optical band gap obtained from the PC measurements was well described by Eg(T)=2.7116 eV−(7.65×10−4 eV/K)T2/(425+T). However, the behavior of the PC was different from that generally observed in other semiconductors. The PC intensities decreased with decreasing temperature. This phenomenon had ever been reported in a PC experiment on bulk crystals grown by the Bridgman method. From the relation of log Jph vs 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. Consequently, the trapping centers due to native defects in the CdIn2S4 film were suggested to be the cause of the decrease in the PC signal with decreasing temperature. CdIn2S4 (110) films were grown on semi-insulating GaAs (100) by a hot wall epitaxy method. Using photocurrent (PC) measurements, the PC spectra in the temperature range of 30 to 10 K appeared as three peaks in the short wavelength region. It was found that three peaks, A-, B-, and C-excitons, correspond to the intrinsic transition from the valence band states of Γ4(z), Γ5(x), and Γ5(y) to the exciton below the conduction band state of Γ1(s), respectively. A 0.122 eV crystal field splitting and the 0.017 eV spin orbit splitting were obtained. Thus, the temperature dependence of the optical band gap obtained from the PC measurements was well described by Eg(T)=2.7116 eV−(7.65×10−4 eV/K)T2/(425+T). However, the behavior of the PC was different from that generally observed in other semiconductors. The PC intensities decreased with decreasing temperature. This phenomenon had ever been reported in a PC experiment on bulk crystals grown by the Bridgman method. From the relation of log Jph vs 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. Consequently, the trapping centers due to native defects in the CdIn2S4 film were suggested to be the cause of the decrease in the PC signal with decreasing temperature.

Optoelectrical properties of ZnO thin films grown by pulsed laser deposition

홍광준,Changsun Park 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.4

ZnO films on Al2O3 substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and Xray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was 0.201o. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be 299 cm2/ V s and 8.27×1016 cm−3, respectively. The absorption spectra revealed that the temperature dependence of the optical band gap on the ZnO films was Eg(T)=3.4393 eV−(5.30×10−4 eV/K)T2/(367+T). ZnO films on Al2O3 substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and Xray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was 0.201o. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be 299 cm2/ V s and 8.27×1016 cm−3, respectively. The absorption spectra revealed that the temperature dependence of the optical band gap on the ZnO films was Eg(T)=3.4393 eV−(5.30×10−4 eV/K)T2/(367+T).

Raman scattering and temperature-dependent photoluminescence properties of CdS/GaAs epilayers grown by hot-wall epitaxy

홍광준,T.S.Jeong,윤창주 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2

Hexagonal-structured CdS/GaAs epilayers were grown by the hot-wall epitaxy method. From the Raman spectrum, we found that the exciton-phonon coupling is deeply related to the dimensionality. The optical properties attributed to the thermal quenching phenomenon of CdS were studied through photoluminescence (PL) measurements as a function of temperature. With an increase in the temperature, PL intensities of free excitons were exponentially reduced and their spectral width showed a tendency to broaden. This tendency is related to the phonons generated by the lattice vibration of the host material in CdS. These findings led us to conclude that the phonons may be participating in the quenching process. Also, the temperature dependence of the band gap energy of CdS was well interpreted by E g(T) = 2.5684 − (5.4 × 10−4)T2/(258.8 + T).

펄스 레이저 증착(PLD)법에 의한 ZnO 박막 성장과 열처리 효과

홍광준 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.5

ZnO epilayer were synthesized by the pulsed laser deposition(PLD) process on $Al_2$ $O_3$substrate after irradiating the surface of the ZnO sintered pellet by the ArF(193 nm) excimer laser. The epilayers of ZnO were achieved on sapphire(A $l_2$ $O_3$) substrate at a temperature of 400 $^{\circ}C$. The crystalline structure of epilayer was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are 8.27${\times}$$10^{16}$$cm^{-3}$ and 299 $\textrm{cm}^2$/Vㆍs at 293 K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, $E_{g}$(T)= 3.3973 eV - (2.69 ${\times}$ 10$_{-4}$ eV/K) $T^2$(T+463k). After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{Zn}$ , $V_{o}$ , Z $n_{int}$, and $O_{int}$ obtained by PL measurements were classified as a donors or accepters type. In addition, we concluded that the heat-treatment in the oxygen atmosphere converted ZnO thin films to an optical p-type. Also, we confirmed that vacuum in ZnO/A $l_2$ $O_3$did not form the native defects because vacuum in ZnO thin films existed in the form of stable bonds.s.s.s.

Hot Wall Epitaxy(HWE)법에 의한 $CulnSe_2$ 박막 성장과 특성

홍광준,이상열,박진성 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.6

The stochiometric mix of evaporating materials for the CuInSe$_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CuInSe$_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy(HWE) system. The source and substrate temperature were 62$0^{\circ}C$ and 41$0^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of CuInSe$_2$ single crystal thin films measured from Hall effect fby van der Pauw method are 9.62x10$^{16}$ cm$^{-3}$ , 296$\textrm{cm}^2$/V.s at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the CuInSe$_2$ single crystal thin film we have found that he values of spin orbit splitting ΔSo and the crystal field splitting ΔCr were 6.1 meV and 175.2 meV at 10K, respectively. From the photoluminescence measurement on CuInSe$_2$ single crystal thin film we observed free excition (Ex) existing only high quality crystal and neutral bound exiciton (D$^{\circ}$,X) having very strong peak intensity. Then, the full-width-at-half-maximum(FWHM) and binding energy of neutral donor bound excition were 7meV and 5.9meV, respectivity. by Haynes rule, an activation energy of impurity was 50 meV.

Hot Wall Epitaxy(HWE)법에 의한 Cdln₂S₄ 단결정 박막 성장과 열처리 효과

홍광준,이관교 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.11

A stoichiometric mixture of evaporating materials for CdIn$\_$2/S$\_$4/ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CdIn$\_$2/S$\_$4/ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were 630 $\^{C}$ and 420 $\^{C}$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of CdIn$\_$2/S$\_$4/ single crystal thin films measured from Hall effect by van der Pauw method are 9.01$\times$10$\^$16/ cm$\^$-3/ and 219 ㎠/V$.$s at 293 K, respectively. From the optical absorption measurement, the temperature dependence of energy band gap on CdIn$\_$2/S$\_$4/ single crystal thin films was found to be Eg(T) = 2.7116 eV - (7.74 $\times$ 10$\^$-4/ eV) T$\^$2//(T+434). After the as-grown CdIn$\_$2/S$\_$4/ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of CdIn$\_$2/S$\_$4/ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of V$\_$cd/, V$\_$s/, Cd$\_$int/ and S$\_$int/ obtained by PL measurements were classified as donors or accepters type. And we concluded that the heat-treatment in the S-atmosphere converted CdIn$\_$2/S$\_$4/ single crystal thin films to an optical p-type. Also, we confirmed that In in CdIn$\_$2/S$\_$4/GaAs did not from the native defects because In in CdIn$\_$2/S$\_$4/ single crystal thin films existed in the form of stable bonds.

HWE 방법에 의한 CdS 박막의 성장과 광전도 특성

홍광준 한국결정성장학회 1996 韓國結晶成長學會誌 Vol.6 No.3

HWE 방법으로 CdS 박막을 quartz plate 위에 성장하였다. CdS 박막을 성장할 때 증발원과 기판의 온도를 각각 $590^{\circ}C$, $400^{\circ}C$로 하였고 성장된 두께는 $2.5\;\mu\textrm{m}$였다. 성장된 CdS 박막의 X-선 회절 무늬로부터 외삽법에 의해 구한 a와 c는 각각 $4.137\;{\AA}$과 $6.713\;{\AA}$인 육방정계임을 알았다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자 농도와 이동도의 온도 의존성을 연구하였다. 이동도는 30 K에서 200 K까지는 piezoelectric 산란에 기인하고, 200 K에서 293 K까지는 polar optical 산란에 의하여 감소하였다. 광전도 셀의 특성으로 spectral response, 최대 허용 소비전력 (MAPD), 광전류와 암전류비 (pc/dc), 및 응답시간을 측정하였다. Cu 증기 분위기에서 열처리한 광전도 셀의 경우 ${\gamma}=0.99,\;pc/dc=9.42{\times}10^{6}$, MAPD : 318 mW, rise time 10 ms, decay time 9 ms로 가장 좋은 광전도 특성을 얻었다. The CdS thin films are grown on quartz plate by hot wall epitaxy. The source and substrate temperature is $590^{\circ}C$ and $400^{\circ}C$ respectively, and thickness of the film is $2.5\;\mu\textrm{m}$. Using extrapolation method of X-ray diffraction patterns for the CdS thin film, it was found hexagonal structure whose lattice constant a and c were $4.137\;{\AA}$ and $6.713\;{\AA}$, respectively. Hall effect on this sample was measured by the method of van der Pauw and studied on cattirer density and mobility depending on temperature. From hall data, the mobility was likely to be decreased by piezoelectric scattering in the temperature range 30 K to 200 K and by polar optical scattering in the temperature range 200 K to 293 K. In order to explore the applicability as a photoconductive cell we measured the sensitivity ($\gamma$), the ratio of photocurrent to darkcurrent (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time. The results indicated that for the samples annealed in Cu vapor the photoconductive characteristics are the best. Then we obtained the sensitivity of 0.99, the value of pc/dc of $9.42{\times}10^{6}$, the MAPD of 318 mW, and the rise and decay time of 10 ms and 9 ms, respectively.

Hot wall epitaxy(HWE)법에 의한 ZnAl₂Se₄단결정 박막 성장과 광학적 특성

홍광준 한국물리학회 2011 새물리 Vol.61 No.8

A stoichiometric mixture of evaporating materials for ZnAl₂Se₄single crystal thin films was prepared in a horizontal electric furnace. The ZnAl₂Se₄ polycrystals had a defect chalcopyrite structure, with lattice constants _0= 5.5563Å, c_0 = 10.8897Å. To obtain a single-crystal thin film, We deposited mixed ZnAl₂Se₄ crystals on a thoroughly-etched semi-insulating GaAs(100) substrate by using a hot-wall epitaxy (HWE) system. The source and the substrate temperatures were 620℃and 400℃,respectively. The crystalline structure of the single-crystal thin film was investigated by using double-crystal X-ray rocking curves and X-ray diffraction ω-2Θ scans. The carrier density and the mobility of the ZnAl₂Se₄single-crystal thin film were 8.23×10^(16)cm^(-3) and 287m²/v‧s at 293K, respectively. To identify the band gap energy, We investigated the optical absorption spectra of the ZnAl₂Se₄single-crystal thin film in the temperature region of 10-293 K. The temperature dependence of the direct optical energy gap is well presented by the Varshni's relation, E_g(T) =E_g(0) -(αT²/T+β). The constants of Varshni's equation were E_g (0)= 3.5269 eV, α= 2.03×10^(-3) eV/K and β= 501.9 K for the ZnAl₂Se₄single-crystal thin film. 단결정 성장용 ZnAl₂Se₄ 다결정을 수평 전기로에서 합성하였으며,결정구조는 defect chalcopyrite이고 격자상수 α_0= 5.5563Å,c_0 = 10.8897Å이었다. ZnAl₂Se₄단결정 박막은 hot wall epitaxy (HWE) 방법으로 반절연성 GaAs(100)기판에 성장시켰다. MgGa₂Se₄단결정 박막의 성장 조건은 증발원의 온도 620℃, 기판의 온도 400℃였고 성장 속도는0.5㎛/hr였다. ZnAl₂Se₄ 단결정 박막의 결정성은 이중 결정X-선 회절곡선의 반치폭과 X-선 회절무늬의 ω-2Θ로부터구하여 최적 성장 조건을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.23×10^(16)cm^(-3), 287m²/v‧s였다.ZnAl₂Se₄/SI (Semi-Insulated) GaAs(100)단결정 박막의 광흡수 스펙트럼을 10 K에서 293 K까지 측정하였다. 광흡수 스펙트럼으로부터 구한 에너지 간격 E_g(T)는 Varshni 관계식E_g(T) = E_g(0) -(αT²/T+β)을 잘 만족함을알 수 있었다. 이 때 E_g (0)= 3.5269 eV, α= 2.03×10^(-3) eV/K 그리고 β= 501.9 K 이었다.