Title :
Impact Ionization Coefficients in 4H-SiC by Ultralow Excess Noise Measurement
Author :
Green, James E. ; Loh, Wei Sun ; Marshall, Andrew R J ; Ng, Beng Koon ; Tozer, Richard C. ; David, John P R ; Soloviev, Stanislav I. ; Sandvik, Peter M.
Author_Institution :
Dept. of Electron. & Electr. Eng., Univ. of Sheffield, Sheffield, UK
fDate :
4/1/2012 12:00:00 AM
Abstract :
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.
Keywords :
avalanche photodiodes; ionisation; absorption; avalanche photodiodes; electron ionization coefficient; generation profile; hole injection measurement; impact ionization coefficient; mixed injection measurement; multiplication regions; noise factor; pure injection condition; pure-hole-initiated photomultiplication; ultralow excess noise measurement; Absorption; Charge carrier processes; Ionization; Neodymium; Noise; Noise measurement; Photoconductivity; 4H-SiC; Avalanche multiplication; avalanche photodiode (APD); excess noise; impact ionization; local model;
Journal_Title :
Electron Devices, IEEE Transactions on
DOI :
10.1109/TED.2012.2185499