An AlGaAs/InGaAs HEMT Grown on Si Substrate with Ge/GexSi1-x Metamorphic Buffer Layers
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1068-C02-03
An AlGaAs/InGaAs HEMT Grown on Si Substrate with Ge/GexSi1-x Metamorphic Buffer Layers Edward Yi Chang1, Yueh-Chin Lin1, Yu-Lin Hsiao1, Y.C. Hsieh1, Chia-Yuan Chang1, Chien-I Kuo1, and Guang-Li Luo2 1 Department of Materials Science and Engineering, National Chiao-Tung University, 1001 Ta-Hsueh Rd., Hsin-Chu, 30010, Taiwan 2 National Nano Device Laboratories, No 26, Prosperity Road 1, Science-based Industrial Park, Hsin-Chu, 30078, Taiwan ABSTRACT An AlGaAs/InGaAs HEMT grown on Si substrate with Ge/GexSi1-x buffer is demonstrated. The Ge/GexSi1-x metamorphic buffer layer used in this structure was only 1.0 µm thick. The electron mobility in the In0.18Ga0.82As channel of the HEMT sample was 3,550 cm2/Vs. After fabrication, the HEMT device demonstrated a saturation current of 150 mA/mm and a maximum transconductance of 155 mS/mm. The well behaved characteristics of the HEMT device on the Si substrate are believed to be due to the very thin buffer layer achieved and the lack of the antiphase boundaries (APBs) formation and Ge diffusion into the GaAs layers. Index Terms: HEMT, GaAs on Si, SiGe buffer layer. INTRODUCTION The heteroepitaxial growth of III-V materials on Si substrate has attracted great attention in recent years due to its potential of integrating Si and III-V based devices on the same platform. The physical gate length of Si transistors used in the current generation node is about 50 nm. The size of the transistor will reach 10 nm in 2011. In order to extend Moore’s law well into the next decade, Si-CMOS incorporated with III-V semiconductor compound materials in the device structure is one of the promising solutions for the CMOS technology [1]. However, the two main problems to overcome in growing GaAs on Si by heteroepitaxy are the large lattice mismatch of 4% and the difference in the thermal expansion coefficients (63%) of these two materials. To achieve high quality device structures, it is necessary to reduce the dislocations density in the epitaxial GaAs layer. Si+ pre-ion-implantation combined with a GexSi1-x metamorphic buffer structure for the growth of Ge layer on Si substrate was proposed [2]. Enhanced strain relaxation of the GexSi1-x metamorphic buffer layer on Si substrate was achieved due to the introduction of the point-defects by heavy dose Si+ pre-ion-implantation. Because of the strain relaxation enhancement and the interface-blocking of the dislocations in the GexSi1-x metamorphic buffer structure, many threading dislocations was trapped at the heterojunction interface and the total thickness of the Ge/GexSi1-x buffer layers needed for the growth of GaAs on Si was only 1.0 µm. Another problem is the formation of the antiphase boundaries (APBs) at the GaAs/Ge interface, which occur when growing polar GaAs on nonpolar Ge. Several models were reported for the suppression of APBs by using Ge wafer which is 6o off (100) toward direction. This is because as the GaAs epitaxial layer growth proceeds, the initial nuclei grown at the steps coalesce so that APBs-free GaAs can be ach
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