Growth of AlGaN/GaN HEMTs on 3C-SiC/Si(111) Substrates
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1068-C04-05
Growth of AlGaN/GaN HEMTs on 3C-SiC/Si(111) Substrates Yvon Cordier1, Marc Portail1, Sébastien Chenot1, Olivier Tottereau1, Marcin Zielinski2, and Thierry Chassagne2 1 CNRS-CRHEA, rue Bernard Gregory, Sophia Antipolis, Valbonne, 06560, France 2 Novasic, Savoie Technolac, Arche Bât. 4, BP 267, Le Bourget du Lac, 73375, France ABSTRACT In this work, we study cubic SiC/Si (111) templates as an alternative for growing GaN on silicon. We first developed the epitaxial growth of 3C-SiC films on 50mm Si(111) substrates using chemical vapor deposition. Then, AlGaN/GaN high electron mobility transistors were grown by molecular beam epitaxy on these templates. Both the structural quality and the behavior of transistors realized on these structures show the feasibility of this approach. INTRODUCTION Gallium Nitride (GaN) based epitaxial films are widely used in light emission applications, but other applications like high power electronics benefit from the electron transport properties and the high critical electrical field of this wide band gap material. If high frequency electronics are mainly based on AlGaN/GaN High Electron Mobility Transistor heterostructures (HEMT) grown on highly resistive or semi-insulating substrates (silicon carbide (SiC) [1,2], silicon (Si) [3,4], Sapphire, free-standing GaN [5]), applications like power switching often rely on vertical structures grown on conductive substrates. Both of these applications necessitate to sustain high operating voltages and to dissipate the heat generated under high current density. For these reasons, hexagonal silicon carbide (4H-SiC or 6H-SiC) is often preferred due to a superior thermal conductivity as compared to sapphire or silicon substrates. Nevertheless, silicon is inexpensive and available in large size, high volume and the realization of GaN based high performance RF devices has been demonstrated on such a substrate. However, the high reactivity of silicon with the different compounds frequently used for the growth of nitrides (Ga, Al, H2, NH3…) makes the substrate preparation and the nucleation more delicate [6] than on a substrate like SiC, and GaN on Si suffers from a risk of crack generation due to the tensile stress induced by the large lattice mismatch (17%) and thermal expansion coefficient difference between GaN and Si. Cubic SiC (3C-SiC) presents a closer lattice mismatch with GaN (3% for the hexagonal phase of GaN) and a thermal expansion coefficient of 4.5x10-6 K-1 intermediate between the ones of GaN 5.6x10-6 K-1 and Si (3.6x10-6 K-1). (001) oriented self supported 3C-SiC substrates have been used for growing cubic GaN based heterostructures [7]. On the other hand, (111) oriented cubic SiC can be employed as an intermediate layer for the growth of hexagonal phase GaN on Si. The suppression of crack generation in GaN grown on 3C-SiC/Si [8,9] as well as an enhancement of GaN crystal quality as compared with similar structures grown on Si [10,11] have been reported.
Schottky diodes with a reverse breakdown voltage exceeding -250V have
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