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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.
곽준섭,Yongjo Park 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1
In order to develop transparent contacts for InGaN-based light emitting diodes (LEDs), we investigated the eects of the ambient gas (N2 or O2) during annealing of Ni/Au contacts on the contact resistivity, the light transmittance, and the performance of LEDs. The minimum contact resistivity of the Ni/Au contacts annealed in O2 was 8.9 10က4 cm2, which was much lower than that of the contacts annealed in a N2 ambient (6.1 10က3 cm2). The lower contact resistivity of the oxidized Ni/Au contacts was explained by both the formation of NiO and an enhanced outdiusion of H during annealing in the O2 ambient. The oxidized Ni/Au contacts produced a high light transmittance of 90 % at 470 nm. The LEDs with the oxidized Ni/Au contacts showed a two times higher output power and a lower operating voltage at 20 mA compared with those for contacts annealed in a N2 ambient.
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