InP HEMT Technology and Applications

Doctoral thesis, 2004

Indium phosphide high electron mobility transistors (InGaAs/InAlAs/InP HEMTs) exhibit the highest cut-off frequencies and the lowest microwave noise figures of all transistor technologies. Both InP HEMT technology and associated circuit demonstrators are therefore interesting to explore further. In this work, InP HEMTs have been demonstrated on different epitaxial structures, mainly lattice-matched InGaAs/InAlAs/InP, but also on materials containing phosphorus and high indium concentration layers. Device results include a single delta doped 0.14-mm HEMT with a current gain cut-off frequency (fT) of 135 GHz and a power gain cut-off frequency (fmax) of 265 GHz obtained on a lattice-matched material with an InP etch stop layer. Recent progress in the gate process technology has enabled 50 nm gate-length devices to be fabricated routinely on pseudomorphic In0.65Ga0.35As/In0.40Al0.60As/InP material with fT and fmax values in excess of 260 GHz and 310 GHz respectively. Passive components designed for monolithic integration have also been developed and evaluated. Thin film resistors (TFRs) and metal-insulator-metal (MIM) capacitors have been investigated using reactive sputtering. Results include 85 ?/square tantalum nitride TFRs and 300 pF/mm2 silicon nitride MIM capacitors. Special attention has been paid to the modeling of MIM capacitors. Two new models based on transmission line theory are proposed and compared with a generally accepted model. The components have been integrated into an MMIC fabrication process. Successful demonstration of the MMIC process capability has been accomplished in a broadband amplifier. A single-stage resistive feedback amplifier exhibited more than 8-dB gain over a 0—42 GHz band at a DC power of 19 mW. Cryogenic performance of lattice matched 0.12-?m HEMTs has been evaluated in low-noise amplifiers (LNAs). A 4—8 GHz LNA exhibited an average noise temperature of 3.9 K at 15 K ambient temperature. Similarly, an average noise temperature of 1.5 K for a 2—4 GHz amplifier was obtained.