260 GHz F/sub T/, 280 GHz f/sub MAX/ AlSb/InAs HEMT technology

Abstract

In this paper, we report AlSb/InAs HEMT high frequency perfornance up to 260 GHz fT. The 0.1-um gate length and 80-um total gate periphery devices exhibited a small-signal available gain of 10 dB at 100 GHz, and extrapolated fT and fmAx performance of 260 and 280 GHz, respectively at a drain voltage of 0.4 volts and drain current of 18 mA. To the best of our knowledge, this is the highest reported combination of simultaneous fT & fMAx reported for InAs-channel HEMTs. This fT result represents a significant improvement from our previously reported simultaneous fT and fMAx performances for AlSb/InAs HEMT's [1,2]. Particularly, in comparison to previous simultaneous fT and fMAx results of 220 and 275 GHz [2] small-signal model extractions indicate that the improvement in fT is attributed to a 23% reduction in gate-source capacitance from 65 fF to 50 fF. A low-field mobility of 26,300 cmN2/V-s was measured prior to fabrication by a Leheighton LEI 1600 contactless Hall measurement system. We have compared the mobility values measured from fabricated Hall effect structures and contactless Hall measurements prior to fabrication on other wafers grown with the same AlSb/InAs epitaxial profile. The Hall effect structures provide measured mobility over 3000 cmN/V-s greater than measurements by the contactless method. AlSb/InAs HEMTs offer more than two times increases in lowfield electron mobility and saturated electron velocity than InGaAs channel HEMTs, making them well suited for low power and high frequency amplifier applications for submillimeter wave frequencies and below. We have achieved excellent uniformity of device and circuit results on AlSb/InAs structures grown by molecular beam epitaxy (MBE) on semi-insulating 3" GaAs substrates. The uniformity of device characteristics is comparable to those of mature, production InAlAs/InGaAs HEMT's on 3" InP substrates. Electron beam lithography was utilized to fabricate 0.1 um Mo/Au T-gates in a 2 um source-drain region. The source to gate distance was 0.8 um. The devices were passivated with SiN and fabricated with two levels of interconnect metal including airbridges, 300 pF/mm2 doublelayer MIM capacitors, and 100-Ohm/sq precision NiCr resistors for circuit demonstration. We will discuss the development of state-of-the-art AlSb/InAs HEMT circuits at X-band and W-band.