Improvement of 0.1 mu m-gate InGaAs/AlGaAs HEMT performance by suppressionof electro-chemical etching in deionized water

The recess gate region of 0.1 mu m-gate InGaAs/AlGaAs HEMT is anomalously e tched during the deionized water rinsing. When the Au-based ohmic electrode s and GaAs on recess gate region are simultaneously exposed to deionized wa ter, the electro-chemical etching occurs resulting in a non-flat recessed g ate profile. Also, the U-shaped etched groove is formed besides the Al/Ti g ate after the lift-off process due to the electro-chemical etching effect b etween the Al/Ti and GaAs. Such an electro-chemical etching effect is stron gly related to dissolved oxygen in deionized water, which causes OH- ion by the electro-chemical reaction with H2O. The reduction of dissolved oxygen in deionized water suppresses the electro-chemical etching phenomenon. Usin g the deionized water with reduced dissolved oxygen, device performance of the 0.1 mu m-gate InGaAs/AlCaAs HEMT was improved and the current gain cut- off frequency as high as 104 GHz has been obtained. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.