Numerical modeling of heterojunctions including the thermionic emission mechanism at the heterojunction interface

A numerical model for heterojunctions is discussed in which current transport across the heterojunction interface is taken into account by using thermionic emission current in series with drift-diffusion current in the bulk. The thermionic emission current is regarded as a boundary condition, which is used to obtain a relationship between quasi-Fermi-levels on both sides of the interface. GaAs-AlGaAs heterojunctions are simulated as an example, and the results are compared with those obtained by a conventional diffusion model in which current transport across the heterojunction interface is not considered explicitly. It is shown that the thermionic emission mechanism is important and should be considered, particularly in isotype heterojunctions. With the present model, more general numeral analyses that include thermionic emission, drift, and diffusion phenomena can be achieved