Current Collapse and High-Electric-Field Reliability of Unpassivated GaN/AlGaN/GaN HEMTs

• Published in: IEEE transactions on electron devices Vol. 53; no. 12; pp. 2932 - 2941
• Main Authors: Meneghesso, G., Rampazzo, F., Kordos, P., Verzellesi, G., Zanoni, E.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AlGaN/GaN high-electron-mobility transistors (HEMTs); Applied sciences; device simulation; Electronics; Exact sciences and technology; gate lag; hot-electron degradation; hot-electron stress; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors; Gate current; High strength current; Electric stress; Electron injection; hot-electron stress; Two dimensional model; device simulation; Coatings; Surface treatment; Thin film; Surface effect; Electron traps; High electron mobility transistor; Electric field; hot-electron degradation; High field; Numerical simulation; Leakage current; Hot electron; AlGaN/GaN high-electron-mobility transistors (HEMTs); gate lag; Reliability; Damaging; Passivation
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2006.885681

Long-term ON-state and OFF-state high-electric-field stress results are presented for unpassivated GaN/AlGaN/GaN high-electron-mobility transistors on SiC substrates. Because of the thin GaN cap layer, devices show minimal current-collapse effects prior to high-electric-field stress, despite the fact that they are not passivated. This comes at the price of a relatively high gate-leakage current. Under the assumption that donor-like electron traps are present within the GaN cap, two-dimensional numerical device simulations provide an explanation for the influence of the GaN cap layer on current collapse and for the correlation between the latter and the gate-leakage current. Both ON-state and OFF-state stresses produce simultaneous current-collapse increase and gate-leakage-current decrease, which can be interpreted to be the result of gate-drain surface degradation and reduced gate electron injection. This study shows that although the thin GaN cap layer is effective in suppressing surface-related dispersion effects in virgin devices, it does not, per se, protect the device from high-electric-field degradation, and it should, to this aim, be adopted in conjunction with other technological solutions like surface passivation, prepassivation surface treatments, and/or field-plate gate