New InGaAs/InAlAs Improved Heterojunction Insulated Gate Field Effect Transistors

In recent years heterojunction FETs of many varieties have been investigated for application to high speed electronics. Many of the present day speed records are owned by the Modulation Doped FET (MODFET). While this structure is ideal for discrete high frequency microwave amplifiers, it may prove difficult to use for large scale logic circuits. The HIGFET structure that we have developed combines the demonstrated high speed performance of the InGaAs/InAlAs material system with the threshold voltage uniformity that would enable larger scale logic circuits. The HIGFET process is more demanding than that of the MODFET, however, and has presented some technological challenges. The completed transistors incorporates, for example, sub-micron tungsten air bridge gates patterned by electron beam lithography (EBL) and reactive on etching (RIE). In this talk I will discuss the material and process consideration that have gone into this work and report some device performance data which have been recently measured for discrete devices.