ELIMINATION OF MESA-SIDEWALL GATE LEAKAGE IN INA1AS INGAAS HETEROSTRUCTURES BY SELECTIVE SIDEWALL RECESSING/

Conventional mesa isolation in InAlAs/InGaAs HFET's results in the gat e coming in contact with the exposed channel at the mesa sidewall, for ming a parasitic gate-leakage path. We propose and successfully demons trate a novel and simple method of recessing the channel edge into the mesa sidewall using a succinic-acid-based selective etchant for InGaA s over InAlAs. SEM photographs confirm the recessing of the channel al ong the sidewall. Special heterostructure diodes, designed with varyin g amounts of mesa-sidewall/gate-metal overlap, were fabricated with an d without the sidewall isolation step. Electrical measurements confirm the complete elimination of sidewall leakage on both diodes and HFET' s.