Electric-field induced F− migration in self-aligned InGaAs MOSFETs and mitigation

We report, for the first time, a prominent but fully reversible enhancement in transconductance after applying positive gate stress to self-aligned InGaAs MOSFETs. We attribute this to electric-field-induced migration of fluorine ions (F−) introduced during the RIE gate recess process. F− is known to passivate Si donors in InAlAs. In our device structure, an n-InAlAs ledge facilitates the link from the contacts to the intrinsic device. We use secondary ion mass spectroscopy (SIMS) to independently confirm that our process leads to F pile up at the n-InAlAs layer. Transmission line model (TLM) structures confirm F−-induced donor passivation. The understanding derived has lead us to redesign our InGaAs MOSFETs by eliminating n-InAlAs layers and instead use an n-InP ledge. The new device design not only exhibits greatly improved electrical stability but also record performance.