Influence of AlN Passivation on Dynamic ON-Resistance and Electric Field Distribution in High-Voltage AlGaN/GaN-on-Si HEMTs

• Published in: IEEE transactions on electron devices Vol. 61; no. 8; pp. 2785 - 2792
• Main Authors: Zhikai Tang, Sen Huang, Xi Tang, Baikui Li, Chen, Kevin J.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AlGaN/GaN; AlN; Aluminum nitride; charge compensation; current collapse; Devices; dynamic ON-resistance; Dynamics; electric field distribution; Electric fields; electroluminescence (EL); Gallium nitrides; HEMTs; high electron mobility transistor (HEMT); High electron mobility transistors; high voltage; III-V semiconductor materials; Logic gates; MODFETs; numerical simulations; Passivation; plasma-enhanced atomic layer deposition (PEALD); polarization; pulsed I-V; Semiconductor devices; surface passivation; surface/interface states; Switches; Temperature measurement; numerical simulations; AlN; surface passivation; electric field distribution; current collapse; surface/interface states; charge compensation; dynamic ON-resistance; high voltage; AlGaN/GaN; electroluminescence (EL); plasma-enhanced atomic layer deposition (PEALD); pulsed I – V; polarization; high electron mobility transistor (HEMT)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2014.2333063

We investigate in detail the influence of AlN passivation on dynamic ON-resistance (R ON ) and electric field (E-field) distribution in high-voltage AlGaN/GaN high electron mobility transistors (HEMTs) on a Si substrate based on pulsed I-V measurements, electroluminescence (EL) microscopy, and 2-D physics-based numerical device simulations. It is found that the dynamic RON increase has been significantly suppressed to below 10% at various temperatures ranging from -50 to 200 °C owing to the effective and robust compensation of deep acceptor-like trap states at the AlN/GaN (passivation/cap) interface by the additional positive polarization charges induced in the epitaxial AlN thin passivation layer grown in a plasma-enhanced atomic layer deposition system. To the best of our knowledge, this is the first time that highly suppressed current collapse in an AlGaN/GaN HEMT on a Si substrate within a wide temperature range is ever reported. By monitoring the dynamic RON for 100 consecutive 133-kHz switching cycles, its variation is observed to be less than 2.5%, indicating excellent stability of the passivation effectiveness. The electric field in an AlN-passivated device is found to be well confined at the drain-side gate edge, as shown in EL measurement and numerical simulation results. This phenomenon directly suggests that the virtual gate effect arising from surface trap charging has been effectively alleviated by the AlN passivation technique.