InAlAs/InGaAs/InP dual-gate-HFET's: new aspects and properties

Regardless of the conventional advantages (higher MSG, higher f/sub max/) of the dual-gate HFET-cascode in comparison to its single-gate counterpart, new properties of the three-port device in the InAlAs/InGaAs/InP-system are presented by extended dc- and rf-analysis. The influence of the second gate via V/sub G2S/ on the impact ionization effect is clearly demonstrated. Optimum extrinsic bias conditions offer the possibility to shift impact ionization from the first intrinsic, rf-driven FET to the second FET. S-parameter measurements underline that, at this bias condition, impact ionization does not affect the high frequency behaviour of the whole device. Thus, a drastic improvement of the noise behaviour is demonstrated. In conclusion, the DGHFET-cascode on InP-under the bias condition V/sub G2S/=0 V-instead of its SGHFET-counterpart will be a promising candidate for low noise amplifiers, e.g. in optoelectronic receivers.