SiGe pMODFETs on silicon-on-sapphire substrates with 116 GHz f/sub max/

Abstract

The dc and microwave results of Si 0 2 Ge 0 8 /Si 0 7 Ge 0 3 pMODFETs grown on silicon-on-sapphire (SOS) substrates by ultrahigh vacuum chemical vapor deposition are reported. Devices with = 0 1 m displayed high transconductance (377 mS/mm), low output conductance (25 mS/mm), and high gate-to-drain breakdown voltage (4 V). The dc current-voltage (I-V) characteristics were also nearly identical to those of control devices grown on bulk Si substrates. Microwave characterization of 0 1 50 m 2 devices yielded unity current gain ( ) and unilateral power gain ( max ) cutoff frequencies as high as 50 GHz and 116 GHz, respectively. Noise parameter characterization of 0 1 90 m 2 devices revealed minimum noise figure ( min ) of 0.6 dB at 3 GHz and 2.5 dB at 20 GHz. Index Terms-Germanium alloys, heterojunctions, MODFETs, semiconductor device noise, semiconductor epitaxial layers, silicon alloys, silicon-on-insulator technology. R ECENT advances in SiGe strained-layer modulation-doped field-effect transistor (MODFET) technology indicate that these devices may hold promise for a wide variety of future microelectronic applications, including wireless and wired communications [1], [2], as well as future advanced logic technology [3], [4]. For communications applications in particular, losses and isolation problems due to the conducting Si substrate represent a serious disadvantage compared to III-V devices that utilize semi-insulating substrates, and these problems worsen with increased frequency. The use of insulating substrates such as sapphire is a potential solution to this problem, and previous results on Si [5] and pseudomorphic SiGe-channel MOSFETs [6] fabricated on silicon-on-sapphire (SOS) wafers have produced encouraging results. However, SiGe MODFETs require relaxed SiGe buffer layers, and the growth of high-quality relaxed SiGe on sapphire or SOS substrates has not previously been demonstrated. In this paper, we present the fabrication and characterization of 0.1 m gate-length pMODFETs fabricated on high-mobility Si Ge /Si Ge quantum wells grown on SOS wafers. We show that high-mobility heterostructures can be grown on these Manuscript

Low-frequency noise in buried-channel SiGe n-MODFETs

“…Unlike III-V MODFETs, SiGe MODFETs have the ability to achieve complementary device topologies on the same wafer. High transconductance p-MODFETs with superior high-frequency noise performance have been demonstrated using UHV/CVD [3][4][5]. The broadband noise of SiGe n-MODFETs has been reported in literature [6], and an NF min of 1.6 dB at 20 GHz was reported on SiGe n-MODFETs investigated in this study [7].…”

High electron mobility in SiGe/Si n -MODFET structures on sapphire substrates

“…reported p-MODFET structures on sapphire with room temperature hole mobilities of 800 cm2N-sec; low temperature data was not presented [5]. To the best of our knowledge, no one has reported n-MODFET behavior in SiGelSi structures on sapphire substrates, nor the existence of Shubnikov-de Haas oscillations in SiGe/Si MODFETs (either n-or p-type) deposited on sapphire substrates.…”

High-Electron-Mobility SiGe on Sapphire Substrate for Fast Chipsets

“…SiGe on sapphire is one of the most important approaches to build silicon-germanium on insulator (SGOI) devices such as a high mobility transistor for -band and higher frequency applications up to 116 GHz [6][7][8]. Because sapphire is one of the best insulators, the high frequency parasitic capacitance between the semiconductor layer and the substrate can be alleviated for better performance at high frequency.…”