Thermally stable transparent Ru-Si-O Schottky contacts for n-type GaN and AlGaN
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E3.41.1
Thermally stable transparent Ru-Si-O Schottky contacts for n-type GaN and AlGaN E. Kaminska1, A. Piotrowska1, K. Golaszewska1, R. Lukasiewicz1, A. Szczesny1,2, E. Kowalczyk1, P. Jagodzinski1, M. Guziewicz1, A. Kudla1, A. Barcz1,3, R. Jakiela3 1
Institute of Electron Technology, al. Lotnikow 32/46, 02-668 Warszawa, Poland Warsaw University of Technology, Institute of Microelectronics & Optoelectronics, ul. Koszykowa 75, Warszawa 00-662, Poland 3 Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warszawa, Poland 2
ABSTRACT We have developed the deposition and studied the electrical characteristics and thermal reliability of Ru-based contacts on n- type GaN as well as on AlGaN/GaN heterostructure. Amorphous, conducting and transparent RuSiO4 contacts with their extremely low reverse currents and thermal stability up to 9000C, show great potential for use as Schottky contacts to n-type GaN and gate electrodes for AlGaN/GaN HEMT in high temperature, high power applications as well as in UV detectors. INTRODUCTION The exceptional properties of III-V nitrides such as wide direct bandgap, high thermal conductivity, thermal stability and chemical inertness combined with high concentration, high mobility two-dimensional electron gas offered by AlGaN/GaN interfaces, make them materials of choice for high-power/high-frequency/high-temperature applications. The superior characteristics of GaN-based high electron mobility transistors (HEMTs) over Si and GaAsbased devices have been already demonstrated [1]. At present, the development of high quality, thermally stable Schottky contacts applied as gate electrodes in HEMTs is one of the key issues for the fabrication of high performance, reliable devices. Typically large work function metals such as Pt, Ni and Re as well as refractory silicides and nitrides are applied as Schottky contacts [2,3]. Although they show satisfying electrical properties for optimized deposition processes, after treatment at elevated temperatures their performance deteriorates. Despite the inherent stability of refractory metallizations, thermally activated interactions at the metallization/semiconductor interfaces cause the degradation of the Schottky barriers. Field effect transistors based on GaN and its related heterostructures suffer from surface related problems including drain current collapse and excess gate leakage [4]. A surface passivation process consisting of a suitable surface treatment and the formation of the insulated gate and passivation of the structure can solve these problems [4]. Targeting high temperature applications we have chosen to investigate the behavior of ruthenium based metallizations such as Ru, RuO2 and Ru-Si-O in contact with GaN/AlGaN material system. Both Ru and RuO2 are high melting point materials, characterized by low bulk resistivity and work function exceeding 5 eV. The feasibility of conducting, amorphous ternary Ru-Si-O thin films and their excellent stability against crystallization up to 1000oC have been recently reported b
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