Epitaxial optimization of 130-nm gate-length InGaAs/InAlAs HEMTs for high-frequency applications
Journal article, 2008
In this paper, the influence of epitaxial-layer design on high-frequency properties of 130-nm gate-length InGaAs/InAlAs/InP high-electron-mobility transistors (InP HEMTs) has been investigated. The In channel content ([In]: 53%, 70%, and 80%), the δ-doping concentration (δ: 3, 5, and 7 × 1012 cm-2), and the Schottky-layer thickness (dSL: 9, 11, and 13 nm) have been varied. The maximum frequency of oscillation fmax, the cutoff frequency fT, the drain-to-source current IDS, and the transconductance gm have been analyzed for InP HEMTs. All devices exhibited an increase in IDS with increasing [In], δ, and dSL. An increase in fmax, fT, and gm were observed with increasing [In]. When changing [In] from 53% to 80%, fT and fmax improved by 14% and 21%, respectively. For the δ parameter, an increase in fT and gm was found. However, fmax was drastically reduced for the highest δ. This is suggested to be due to the formation of a parasitic conduction channel located at the doping plane in the HEMT structure for δ ≥ 6.3 × 1012 cm-2. For the dSL parameter, an optimum with respect to fmax, fT, and gm was observed. The optimized HEMT exhibited an extrinsic fT and fmax of 250 and 300 GHz, respectively.