Al ₂O ₃/InSb/Si quantum well MOSFETs having an ultra-thin InSb layer

InSb is one of the most promising candidates for the channel layers of the post scaling LSIs, because it features highest electron mobility of 78,000 cm ²/(Vs) and highest saturation velocity of 5×10 ⁷ cm/s among III-V compound semiconductors. High performance HEMTs based on InSb/InAlSb material system have been already demonstrated [1]. However, growth of high quality InSb on Si is difficult due to the large lattice mismatch of 19.3%. We have recently demonstrated that good InSb epitaxial films can be grown on Si (111) substrates using novel growth technique [2]. This technique is based on the fact that the InSb layer grown on a Si (111) substrate is rotated by 30 degrees with respect to the substrate under a certain initial condition, which reduces the lattice mismatch to only 3.3 %, as shown in Fig. 1. Very high mobility of 40,000 cm ²/(Vs) with low carrier concentration of 1.8×10 ¹⁶ cm ³ has been obtained using this growth technique for 1-μm-thick films [3]. Moreover, this drastic reduction of the lattice mismatch produces a new possibility, a pseudomorphic InSb/Si quantum well (QW) MOSFETs based on an ultra thin InSb layer grown directly on Si. When the thickness of the InSb channel layer reduces to the critical thickness, such thin channels should have good quality. This has significant advantages, such as elimination of the time-consuming thick buffer layer growth, good electron confinement by the InSb/Si heterojunction. Furthermore it can receive benefits of SOI if one uses SOI substrates. In this paper, we report the fabrication and the properties of Al ₂O ₃/InSb/Si QW MOSFETs having an ultra thin InSb channel layer.