Elimination of mesa-sidewall gate leakage in InAlAs/InGaAs heterostructures by selective sidewall recessing

Conventional mesa isolation in InAlAs/InGaAs HFETs results in the gate coming in contact with the exposed channel at the mesa sidewall, forming a parasitic gate-leakage path. The authors propose a simple method of recessing the channel edge into the mesa sidewall using a succinic-acid-based selective etchant for InGaAs over InAlAs. SEM photographs confirm the recessing of the channel along the sidewall. Special heterostructure diodes, designed with varying amounts of mesa-sidewall/gate-metal overlap, were fabricated with and without the sidewall isolation step. Electrical measurements confirm the complete elimination of sidewall leakage. for both diodes and HFETs.<>