Enhanced Carrier Velocity in 0.08 μm and 0.15 μm Gate-Length MODFET's at 77 K

Abstract

In this paper, we report the results of microwave characterization of 0.08 μm, and 0.15 μm gate-length pseudomorphic (AlGaAs/ψ-InGaAs/GaAs) MODFETs, and 0.15 μm gate-length lattice-matched (InAlAs/InGaAs/InAlAs) MODFETs at 300 K and 77 K. Corresponding an effective gate length of∼0.18 μm, the effective carrier saturation velocity (v_sat) has been calculated to be 3.4 × 10⁷ cm/sec for the 0.08 μm gate-length pseudomorphic MODFET at 300 K. At 77 K, due to the lower barrier height and possible real space transfer of energetic electrons into the upper AlGaAs layer, in the 0.08 μm and 0.15 μm pseudomorphic MODFETs an accurate determination of the carrier velocity has not been possible. In the case of the lattice-matched 0.15 μm gate-length MODFET's, the extracted values of v_sat, have been found to be 4.1 × 10⁷ cm/sec and 6.2 × 10⁷ cm/sec at 300 K, and 77 K, respectively.

Indexing term:

• Microwave characterisation
• MODFET