High-current 0.15-μ-gate enhancement-mode high-electron mobility transistors utilizing Ir/Ti/Pt/Au gate metallization were fabricated using a new process including a high-temperature gate anneal that is required for Schottky-barrier height enhancement for the Ir-based gate contact. SiNx encapsulation was employed to prevent thermal degradation of device layer during the high-temperature gate anneal. Excellent enhancement-mode operation, with a threshold voltage of 0.1 V and IDSS of 2.1 mA/mm, was realized. Both the annealed and unannealed devices exhibited high gm,max and ID,max 800 mS/mm and 430 mA/mm, respectively. A unity current-gain cutoff frequency fT of 151 GHz and a maximum oscillation frequency fMAX of 172 GHz were achieved. From the dc and RF characteristics, it can be deduced that there was no degradation of the gate contact and the heterostructure due to gate annealing. Furthermore, it was found that the gate diffusion during gate annealing was negligible since no increase in gm,max was observed.
- Enhancement-mode high-electron mobility transistor (E-HEMT)
- InP E-HEMT
- Iridium gate
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering