Epitaxial Optimization of 130-nm Gate-Length InGaAs/InAlAs/InP HEMTs for Low-Noise Applications

Abstract

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 delta-doping concentration (delta: 3, 5, and 7 times 1012 cm-2), and the Schottky layer thickness (dSL: 9,11, and 13 nm). All HEMTs exhibited low gate-leakage current IG below 1 muA/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 delta was observed with respect to minimum noise figure NFmin. Increasing [In] only provided a slight reduction in N-Fmin. In contrast, the RF performance was much more affected by increasing [In]. The lowest NFmin was achieved with a delta doping of 5 times 1012 cm2 and a dSL of 11 nm.