Linearity Improvement With AlGaN Polarization- Graded Field Effect Transistors With Low Pressure Chemical Vapor Deposition Grown SiN_x Passivation

Abstract

In this letter, we discuss the application of low pressure chemical vapor deposition (LPCVD) grown SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation-first process to improve the power density and linearity performance of a metal oxide chemical vapor deposition (MOCVD) grown AlGaN channel polarization-graded field-effect transistor (PolFET). Significantly improved dispersion behavior was observed compared to plasma enhanced chemical vapor deposition (PECVD) grown SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation. The Current collapse at 30 V drain quiescent condition for pulsed I-V was reduced to 8% (LPCVD) from 25% (PECVD). 10 GHz load-pull measurement showed a maximum output power density of 3.4 W/mm with a peak power added efficiency (PAE) of 40%. Two-tone intermodulation distortion measurement at 10 GHz for devices with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150\boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> width revealed an OIP3 of 39 dBm and an excellent corresponding linearity figure of merit OIP3/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{{\textit {DC}}}$ </tex-math></inline-formula> of 13.3 dB. This is the best device level OIP3/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{{\textit {DC}}}$ </tex-math></inline-formula> reported to date at X-band for III-Nitride microwave transistors.