Elimination of Mesa-Sidewall Gate Leakage in InAlAs/InGaAs Heterostructures bySelective Sidewall Recessing

摘要

Conventional mesa isolation in InAlAs/InGaAs HFET's results in the gate coming incontact with the exposed channel at the sidewall, forming a parasitic gate-leakage path. We propose and successfully demonstrate a novel and 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 on both diodes and HFET'S.