Reduced Contact Resistance and Improved Transistor Performance by Surface Plasma Treatment on Ohmic Regions in AlGaN/GaN HEMT Heterostructures

Abstract

A significantly reduced contact resistance and an improved DC and RF performance is demonstrated for AlGaN/GaN high electron mobility transistors by surface plasma treatments on ohmic regions in GaN‐based heterostructures. Various plasma processes using BCl 3 , Cl 2 , Ar, SF 6 , and their combinations are considered. While it is known that certain plasma treatments can remove native oxide and thereby reduce the ohmic contact resistance, detailed experiments are performed to further enhance the understanding. In addition, a second aspect of the plasma treatment is shown, where the controlled physical component of the etching process can improve the AlGaN surface morphology. This in turn can reduce the tunneling resistance for the carriers from the alloyed contact to the two‐dimensional electron gas. The contact resistance is found to decrease to 0.10 from 0.65 Ω mm for Ar, Cl 2 , and BCl 3 treated sample in comparison to that of the control sample. The corresponding transconductance, saturation drain current, and unity current gain frequency are found to increase by 30, 37, and 41% for the high electron mobility transistors fabricated on the same sample.