• Humphreys, Colin
• Chalker, P. R.
• Lee, K. B.
• Cho, S. J.
• Thayne, Iain
• Wallis, D.
• Guiney, I.
• Roberts, Joseph
• Houston, P. A.

Abstract

<jats:p>We report the modification and control of threshold voltage in enhancement and depletion mode AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors through the use of in-situ fluorine doping of atomic layer deposition Al2O3. Uniform distribution of F ions throughout the oxide thickness are achievable, with a doping level of up to 5.5 × 1019 cm−3 as quantified by secondary ion mass spectrometry. This fluorine doping level reduces capacitive hysteretic effects when exploited in GaN metal-oxide-semiconductor capacitors. The fluorine doping and forming gas anneal also induces an average positive threshold voltage shift of between 0.75 and 1.36 V in both enhancement mode and depletion mode GaN-based transistors compared with the undoped gate oxide via a reduction of positive fixed charge in the gate oxide from +4.67 × 1012 cm−2 to −6.60 × 1012 cm−2. The application of this process in GaN based power transistors advances the realisation of normally off, high power, high speed devices.</jats:p>

Topics

• semiconductor
• forming
• spectrometry
• secondary ion mass spectrometry
• atomic layer deposition