Impact Ionization Coefficients in 4H-SiC by Ultralow Excess Noise Measurement

• Published in: IEEE transactions on electron devices Vol. 59; no. 4; pp. 1030 - 1036
• Main Authors: Green, J. E., Wei Sun Loh, Marshall, A. R. J., Ng, B. K., Tozer, R. C., David, J. P. R., Soloviev, S. I., Sandvik, P. M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 4H-SiC; Absorption; Applied sciences; Avalanche multiplication; avalanche photodiode (APD); Charge carrier processes; Coefficients; Devices; Electronics; Exact sciences and technology; excess noise; impact ionization; Ionization; Ionization coefficients; local model; Multiplication; Neodymium; Noise; Noise factor; Noise measurement; Optoelectronic devices; Photoconductivity; Photodiodes; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Uncertainty; Noise figure; Hole; Ionization coefficient; Low field; Noise factor; Noise measurement; excess noise; Avalanche multiplication; Silicon carbide; Avalanche photodiodes; Optoelectronic device; avalanche photodiode (APD); local model; Impact ionization; 4H-SiC; Charge carrier injection
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2012.2185499

Photomultiplication and excess noise measurements have been undertaken on two 4H-SiC avalanche photodiodes (APDs) using 244-nm light and 325-nm light. The structures are APDs with separate absorption and multiplication regions having multiplication regions of 2.74 and 0.58 μm , respectively. Pure injection conditions in the thicker device permit the measurement of pure-hole-initiated photomultiplication and an excess noise factor. Ionization coefficients for both carrier types have been extracted from these data using a local model. The use of the excess noise factor to infer the value of the less readily ionizing coefficient α from pure hole injection measurements is more robust than direct extraction from mixed injection measurements. This is because mixed injection introduces uncertainty in the generation profile. We report a significant reduction of the electron ionization coefficient α at low fields. The more readily ionizing hole coefficient β remains very similar to prior work.