Electro-Optical Modulation in a 4H-SiC Slab Induced by Carrier Depletion in a Schottky Diode

Electro-optical modulation of a 1550 nm wavelength carrier is observed and characterized in a 4H-SiC epitaxial layer which is part of a 600 V breakdown voltage commercial Schottky diode. Experimental evidence of a phase shift has been obtained within an interferometric structure, however not designed for such purposes. The amplitude modulation is induced both in dc and switching operation by means of plasma dispersion effect, and specifically by carrier depletion of the epitaxial layer, when a reverse bias is applied to the metal/4H-SiC(n)/4H-SiC(n+)/metal vertical rectifying structure. The contribution arising from the electrically induced free-carrier concentration variation yields a figure of merit Vπ × Lπ equal to 53.6 V × cm.