Characterisation of Low Noise 4H-SiC Avalanche Photodiodes
We report photomultiplication, M, and excess noise, F, measurements at 244nm and 325nm in two 4H-SiC separate absorption and multiplication region avalanche photodiodes (SAM-APDs). Sample A is a 4 x 4 array of 16 SAM-APDs. This structure possesses a relatively thin absorption layer resulting in more mixed injection, and consequently higher noise than sample B. The absorption layer of sample B does not deplete, so 244nm light results in >99% absorption outside the depletion region resulting in very low excess noise. Both structures exhibit very low dark currents and abrupt uniform breakdown at 194V and 624V for samples A and B respectively. Excess noise is treated using a local model . The effective ratio of impact ionisation coefficients (keff) is approximately 0.007, this indicates a significant reduction in the electron impact ionisation coefficient, α, compared to prior work [2-5]. We conclude that the value of α will require modification if thick silicon carbide structures are to fit the local model for multiplication and excess noise.
Anton J. Bauer, Peter Friedrichs, Michael Krieger, Gerhard Pensl, Roland Rupp and Thomas Seyller
J. E. Green et al., "Characterisation of Low Noise 4H-SiC Avalanche Photodiodes", Materials Science Forum, Vols. 645-648, pp. 1081-1084, 2010