Mesa avalanche photodiodes (APDs) fabricated on $4H$ silicon carbide ($4H$-$\mathrm{Si}\mathrm{C}$) substrates have consistently produced spatially nonuniform optical responses, particularly at high gain. In this work, we propose that this nonuniformity can be explained by an interplay of several factors: the anisotropic band structure of the hexagonal material, the misalignment between the real-space and reciprocal-space axes induced by the miscut of $4H$-$\mathrm{Si}\mathrm{C}$ substrates, and the nonuniform electric fields of mesa APDs. Through full-band Monte Carlo (FBMC) simulations, field-dependent anisotropic impact ionization coefficients for a range of crystallographic directions between the principal axis ($⟨0001⟩$) and the basal plane ($⟨11\overline{2}0⟩$) are computed. In addition, the field-dependent carrier drift velocities are computed for the principal axis and the basal plane, primarily for model validation. Finally, the same FBMC model used to compute impact-ionization coefficients and drift velocities is used to perform a device simulation of a well-characterized APD for further validation of the model.

Close

PrevNext

View figure in article

• Carrier dynamics
• Crystal structure
• Carbides
• Devices
• Semiconductor compounds
• Wide band gap systems
• Materials modeling
• Monte Carlo methods