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김하술 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.4
We fabricated a flexible white light emitting device by mixing a fabricated zinc sulphide (ZnS) composite (ZnS: Al, Cu, Mn) and polydimethylsiloxane (PDMS) between the thin silver plastic electrodes. The emitted light was analyzed by a spectrometer according to the AC frequency and the applied voltage. The electroluminescence spectrum of the flexible device were measured in the wavelength range of 350 nm ~ 750 nm at the room temperature. By using the deconvolution method, it was confirmed that the measured white light was composed of four superimposed electroluminescent peaks. The CIE color coordinates of the white light were changed according to the applied frequency due to the excitation energy difference. The color coordinate of the observed white light was (0.30, 0.33) at an applied voltage of 200 V at 300 Hz, which is close to the color coordinate value of the ideal white light.
금속 박막 표면의 열처리에 따른 장적외선 대역 표면 플라즈몬 투과 특성
김하술,박현빈,차상준,우정주 한국물리학회 2017 새물리 Vol.67 No.7
We fabricated a plasmonic device for long-wavelength infrared transmission by using semiconductor photolithography and electron-beam evaporation. The maximum long-wavelength infrared transmittance could be adjusted by controlling the lattice period of the aluminum metal film formed on the Si substrate. The diameter of the produced plasmonic device was 3 $\mu$m. When the pitch of the thin film lattice was changed to 5, 5.5, and 6 $\mu$m, the maximum transmittance wavelengths were observed at 15.5, 17, and 18.5 $\mu$m, respectively. In order to investigate the changes in the transmittance characteristics of the plasmonic device due to oxidation of the aluminum thin film, we performed a heat treatment by using a rapid thermal annealing system while supplying a gas mixture of 20% oxygen and 80% nitrogen. After the heat treatment, the root-mean-square roughness of the thin film's surface was increased, as was the oxygen ratio. The maximum transmittance was reduced by 33% and the wavelength at which maximum transmittance was observed was shifted to longer wavelength by about 0.3 $\mu$m after annealing at 300 $^\circ$C. 반도체 포토 리소그래피와 전자빔 증착법을 이용하여 장적외선 투과용 플라즈모닉스 소자를 제작하였다. 장적외선의 최대 투과 파장은 Si 기판 위에 형성된 알루미늄 금속 박막의 격자 주기를 조절함으로써 임으로 변화 시킬 수 있음을 보였다. 플라즈모닉 소자의 알루미늄 박막 구멍 크기를 3 $\mu$m로 고정하고, 주기(pitch)를 5, 5.5, 6 $\mu$m로 변화 시켰을 때 최대 투과도의 파장은 각각 15.5, 17, 18.5 $\mu$m에서 관측 되었다. 알루미늄 박막의 산화에 따른 플라즈모닉스 소자의 투과 특성 변화에 대한 조사를 위하여, 산소 20%와 질소 80%로 구성된 혼합 가스를 공급하면서 급속 열처리기 이용하여 열처리를 하였다. 열처리 후에 박막 표면의 입자 크기의 제곱 평균 제곱근(root mean square) 값이 증가하였으며, 박막 표면의 산소 비율이 높아지는 것을 확인 하였다. 300 $^\circ$C 열처리 후 투과도의 최댓값은 약 33% 감소하였으며, 최대 투과도 값이 장파장 쪽으로 0.3 $\mu$m의 변이가 일어났다.
김하술,S. Myers,B. Klein,A. Kazemi,S. Krishna,Jun Oh Kim,이상준 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.4
The dark current of a type-II InAs/GaSb strained layer superlattice photodiode with an n-i-pstructure is reduced by using an active gate bias technique. To make the gate structure on themesa sidewall of the photodiode, we used Si3N4 and Ti/Au as a dielectric film and a gate metal,respectively. At 77 K, the dark current density of the photodiode with a gate bias (VG = −30 V)applied on the mesa side wall is reduced by more than one order of magnitude compared to the darkcurrent density at zero gate bias. At 77 K, the product of the dynamic differential resistance andthe area at a gate bias of −30 V shows a 12 times improvement compared to the same measurementat zero gate bias.
김하술 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.4
This paper reports the results of modeling of optical and electrical characteristics of InAs/GaSb type II strained layer superlattice (SLS) for the mid-wave infrared detection with n-on-p polarity. The band gap calculation of the SLS was conducted as a function of the InAs and GaSb thickness, using a modified Kronig-Penny model. The cut off wavelength of the fabricated diode was ~ 6 μm (~ 0.2 eV) at 120 K. The product of zero-bias resistance and area (R0A) as a function of an applied bias was investigated in detail to analyze the dark current mechanisms. The thermal diffusion and generation-recombination current were dominant factors under low positive bias. However, as the reverse bias voltage increased, the trap assisted component became one of the dominant dark current factors.
Performance of an InAs/GaSb Type-II Superlattice Photodiode with Si 3 N 4 Surface Passivation
김하술 한국광학회 2021 Current Optics and Photonics Vol.5 No.2
This study observed the performance of an InAs/GaSb type-II superlattice photodiode with a p-i-n structure for mid-wavelength infrared detection. The 10 ML InAs/10 ML GaSb type-II superlattice photodiode was grown using molecular beam epitaxy. The cutoff wavelength of the manufactured photodiode with Si 3 N 4 passivation on the mesa sidewall was determined to be approximately 5.4 and 5.5 µm at 30 K and 77 K, respectively. At a bias of −50 mV, the dark-current density for the Si 3 N 4 -passivated diode was measured to be 7.9 × 10 −5 and 1.1 × 10 −4 A/cm 2 at 77 K and 100 K, respectively. The differential resistance-area product R d A at a bias of −0.15 V was 1481 and 1056 Ω cm 2 at 77 K and 100 K, respectively. The measured detectivity from a blackbody source at 800 K was calculated to be 1.1 × 10 10cm Hz 1/2 /W at zero bias and 77 K.
InAs/GaSb 제2형 응력 초격자 nBn 장적외선검출소자 설계, 제작 및 특성평가
김하술,이훈,Brianna Klein,Nutan Gautam,Elena A. Plis,Stephen Myers,Sanjay Krishna 한국진공학회 2013 Applied Science and Convergence Technology Vol.22 No.6
Long-wave infrared detectors using the type-II InAs/GaSb strained superlattice (T2SL)material system with the nBn structure were designed and fabricated. The band gap energy of the T2SL material was calculated as a function of the thickness of the InAs and GaSb layers by the Kronig-Penney model. Growth of the barrier material (Al0.2Ga0.8Sb) incorporated Te doping to reduce the dark current. The full width at half maximum (FWHM) of the 1st satellite superlattice peak from the X-ray diffraction was around 45 arcsec. The cutoff wavelength of the fabricated device was ∼10.2 μm (0.12 eV) at 80 K while under an applied bias of –1.4 V. The measured activation energy of the device was ∼0.128 eV. The dark current density was shown to be 1.0×10-2 A/cm2 at 80 K and with a bias −1.5 V. The responsivity was 0.58 A/W at 7.5 μm at 80 K and with a bias of −1.5 V. InAs/GaSb 제2형 응력 초격자(strained layer type II superlattice, T2SL)을 이용한 nBn 구조 장적외선 검출소자의 설계 및제작을 하였다. InAs와 GaSb 두께에 따른 T2SL 구조의 장적외선 밴드갭 에너지를 Kronig-Penney 모델을 이용하여 계산하였다. 소자의 암전류 밀도를 줄이기 위해서, nBn 구조에서 장벽층인 Al0.2Ga0.8Sb 성장 중에 Te 보상도핑(compansated doping)을 하였다. 온도(T) 80 K 및 인가전압(Vb) –1.5 V에서, 반응스펙트럼 측정을 통한 소자의 차단파장은 ∼10.2 μm (∼0.122 eV)로 나타났다. 또한 온도 변화에 따른 암전류 측정으로부터 도출된 활성화 에너지는 0.128 eV로 계산 되었다. T=80 K 및 Vb=–1.5 V에서 암전류는 1.0×10-2 A/cm2으로 측정 되었다. 흑체복사 적외선 광원을 이용한 반응도(Responsivity)는 소자 온도 80 K 및 인가전압 –1.5 V의 조건에서 0.58 A/W로 측정되었다.