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Co/GaAs계의 계면반응, 상평형 밑 전기적 특성에 관한 연구
곽준섭,백홍구,신동원,박찬경,김창수,노삼규,Gwak, Jun-Seop,Baek, Hong-Gu,Sin, Dong-Won,Park, Chan-Gyeong,Kim, Chang-Su,No, Sam-Gyu 한국재료학회 1995 한국재료학회지 Vol.5 No.5
Interfacial reactions, phase equilibria and elecrrical properties of Co films on (001) oreinted GaAs substrate, in the temperature range 300-$700^{\circ}C$ for 30min. have been investigated using x-ray diffraction and Augger electron spectropcopy. Cobalt started to react with GaAs at 38$0^{\circ}C$ by formation of Co$_{2}$GaAs phase. At 42$0^{\circ}C$, CoGa and CpAs nucleated at the Co and Co$_{2}$GaAs interface and grew with Co$_{2}$GaAs upto 46$0^{\circ}C$. contacts produced in this annealing regime were rectifying and Schottky varrier heights increased from 0.688eV(as-deposite state) up to 0.72eV(42$0^{\circ}C$). In the subsequent reation, the ternary phase started to decompose and lost stoichiometry at 50$0^{\circ}C$. At higher temperature, Co$_{2}$GaAs disappered and CoGa/CoAs/GaAs layer structures were formed. Contacts produced at higher temperature regime(>50$0^{\circ}C$) showed very low effective barriers. The results of interfacial reactions can be understood from the Co-Ga-As ternary phase diagram.
Al-Based Contacts on Ga-face and N-face n-GaN Wafer Grown by Using Hydride Vapor Phase Epitaxy
곽준섭,Cheolsoo Sone,Jaehee Cho 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
The effect of crystal polarity on the electrical properties of Al-based contacts to the Ga-face and the N-face n-GaN wafer has been investigated. The Al-based contacts prepared on the Ga-face n-GaN wafer exhibited linear I-V characteristics after annealing at 500 C for 90 min. On the contrary, the contacts on the N-face n-GaN wafer showed a nonlinear I-V curve. X-ray photoemission spectroscopy indicated that AlN could be produced at the interface between GaN and the contact metals after the annealing. High-resolution photoemission spectroscopy suggested that the differences in I-V characteristics of the Al-based contacts on the Ga-face and the N-face n-GaN could be explained by opposite piezoelectric fields at the GaN/AlN heterostructure resulting from different polarities of the GaN wafer.먉룮
고농도의 Mg가 도핑된 GaN층을 이용한 GaN계 청자색 레이저다이오드의 동작 전압 감소
곽준섭 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.7
In order to reduce operating voltage of the GaN based blue-violet laser diodes, the effect of highly Mg doped GaN layer, which was grown below ohmic contact metals, on contact resistivity as well as operating voltage has been investigated. The addition of the highly Mg doped GaN layer greatly reduced contact resistivity of Pd/Pt/Au ohmic contacts from $5.2 \times {10}^-2 \Omegaㆍ$\textrm{cm}^2$ to 7.5 \times {10}^-4 \Omegaㆍ$\textrm{cm}^2$$. In addition, it also decreased device voltage at 20 mA by more than 3 V. Temperature- dependent sheet resistivity of the highly Mg doped GaN layer suggested that the reduction of the contact resistivity could be attributed to predominant current flow at the interface between the Pd/Pt/Au contacts and p-GaN through a deep level defect band, rather than the valence band.