Epitaxial optimization of 130 nm gate-length InGaAs/InAlAs/InP HEMTs for low-noise applications
Journal article, 2009
The epitaxial structure of 130-nm gate-length
InGaAs/InAlAs/InP high electron mobility transistors (HEMTs)has been studied in order to optimize the device performance when biased under low-noise conditions. Three essential epitaxial parameters have been varied: the In channel content ([In]: 53%, 70%, and 80%), the δ-doping concentration (δ: 3, 5, and 7 × 1E12 cm−2), and the Schottky layer thickness (dSL: 9, 11, and 13 nm). All HEMTs exhibited low gate-leakage current IG below 1 μA/mm at a low-noise bias, except dSL = 9 nm due to a too thin Schottky layer thickness. It was verified that the lowest noise figure NF was achieved when the square root of the drain-to-source current IDS over transconductance gm exhibited a minimum. A clear optimum for both dSL and δ was observed with respect to minimum noise figure NFmin. Increasing [In] only provided a slight reduction in NFmin. In contrast, the RF performance was much more affected by increasing [In]. The lowest NFmin was achieved with a δ doping of 5 × 1E12 cm−2 and a dSL of 11 nm.