Modeling and Characterization of Current Gain Versus Temperature in 4H-SiC Power BJTs

• Published in: IEEE transactions on electron devices 2010-03, Vol.57 (3), p.704-711
• Main Authors: Buono, B., Ghandi, R., Domeij, M., Malm, B.G., Zetterling, C.-M., Ostling, M.
• Format: Article
• Language: English
• Subjects: 1800 v; Accumulators; Applied sciences; Bipolar junction transistor (BJT); Capture cross sections; Carrier density; Charge carrier lifetime; Collectors; current gain; Current measurement; Doping; Electrical engineering, electronics and photonics; Electrical engineering. Electrical power engineering; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Elektroteknik, elektronik och fotonik; Exact sciences and technology; Gain; interface; interface traps; Ionization; Junctions; Mathematical models; Other multijunction devices. Power transistors. Thyristors; oxide; Power electronics, power supplies; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Semiconductor process modeling; Silicon carbide; silicon carbide (SiC); simulations; TECHNOLOGY; TEKNIKVETENSKAP; Temperature; Temperature measurement; temperature modeling; Transistors
• ISSN: 0018-9383; 1557-9646; 1557-9646
• DOI: 10.1109/TED.2009.2039099

Accurate physical modeling has been developed to describe the current gain of silicon carbide (SiC) power bipolar junction transistors (BJTs), and the results have been compared with measurements. Interface traps between SiC and SiO 2 have been used to model the surface recombination by changing the trap profile, capture cross section, and concentration. The best agreement with measurement is obtained using one single energy level at 1 eV above the valence band, a capture cross section of 1 × 10 -5 cm 2 , and a trap concentration of 2 × 10 12 cm -2 . Simulations have been performed at different temperatures to validate the model and characterize the temperature behavior of SiC BJTs. An analysis of the carrier concentration at different collector currents has been performed in order to describe the mechanisms of the current gain fall-off at a high collector current both at room temperature and high temperatures. At room temperature, high injection in the base (which has a doping concentration of 3 × 10 17 cm -3 ) and forward biasing of the base-collector junction occur simultaneously, causing an abrupt drop of the current gain. At higher temperatures, high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the acting mechanism for the current gain fall-off. Forward biasing of the base-collector junction can also explain the reduction of the knee current with increasing temperature by means of the negative temperature dependence of the mobility.