Study of the Thermal Stability of the Schottky Contacts on GaInP Grown by LP-MOCVD
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STUDY OF THE THERMAL STABILITY OF THE SCHOTTKY CONTACTS ON GaInP GROWN BY LP-MOCVD EDWARD Y. CHANG*, YEONG-LIN LAI**, KUEN-CHYUAN LIN**, CHUN-YEN CHANG**, AND F. Y. JUANG*** *National Chiao Tung University, Institute of Material Science and Engineering, Hsinchu, Taiwan, Republic of China "**National Chiao Tung University, Institute of Electronics, Hsinchu, Taiwan, Republic of China ***Chung Shan Institute of Science and Technology, Lungtan, Taiwan, Republic of China
ABSTRACT Thermal stability of the Schottky contacts on Gao. 5 1Ino. 4 9 P has been made. The Gao. 5 1Ino. 4 9P epitaxial layer was successfully grown on the GaAs substrate by LP-MOCVD to form a lattice-matched heterostructure. In this paper, materials aspects of the Gao. 5 1 Ino. 4 9 P layers were characterized and thermal stability of three different types of films, including singlelayer metal (Pt, Ni, Pd, Au, Co, Mo, W, Cr, Ti, Al, Ta, and In), metal silicides (WSi 2 , W 5 Si 3 , PtSi, and Pt 2 Si), and TiW nitrides (TiWNx) as the Schottky contacts materials on Gao. 51 In0 .4 9 P were studied. Due to the high bandgap nature of Gao. 5 1 lno. 49 P, the Schottky contacts on Gao.5 1 lno.4 9 P demonstrate good characteristics. The barrier heights range from 0.79 to 1.19 eV depending on the selection of the materials and the annealing conditions. For single-metal contacts, Pt film shows the best thermal stability, the barrier height of 1.09 eV and the ideality factor of 1.06 were obtained for the Pt Schottky diode with furnace annealing at 500 CCfor 30 min. For refractory compound films, the TiWNx film shows the best thermal stability. The TiWNx Schottky contacts demonstrate excellent electrical as well as physical characteristics, even after high temperature annealing at 850 9C.
INTRODUCTION Schottky contacts play an important role in the III-V semiconductor devices, such as metal semiconductor field-effect transistors (MESFET's), high electron mobility transistors (HEMT's), microwave mixer diodes, and solar cells. The interest in Ga0 .5 1Ino. 49 P is due to its superior properties on the applications of the optoelectronic and high-speed devices. Because of its wide direct bandgap, this material provides a visible wavelength operation for light emitting diodes (LED's) and laser diodes [1,2] The conduction- and valence-band discontinuities (AEc and AEv) in the Ga0.5 llno.4 9 P/GaAs heterostructures are approximately 0.198 and 0.285 eV, respectively. [3] The valance-band offset of the Gao.lIn0 .4 9 P/GaAs heterojunction is larger than that of Al0 .3 Ga 0 .TAs/GaAs. This large valance-band offset offers the good device performance for n-p-n heterojunction bipolar transistors (HBT's) [4] and p-channel FET's [5]. In this work, we investigated three different types of metal films, including single-layer metal (Pt, Ni, Pd, Au, Co, Mo, W, Cr, Ti, Al, Ta, and In), metal silicides (WSi2 , W 5 Si 3 , PtSi, and Pt 2 Si), and TiW nitrides (TiWNx), as the Schottky contacts matals on the n-type Gao. 5 1 lno.49P. Although the thermal stability of the Schottky contacts o
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