Ansys Insight: Diffusion doping parameters and their meaning
The diffusion doping object in CHARGE allows users to create a realistic doping profile using analytic equations to model the diffused nature of dopants in a doped semiconductor.
The diffusion parameters define the doping profile in the following way:
- dopant type: determines whether the doping is ‘p’ or ‘n’ type.
- surface face: selects the surface through which the dopants enter the doped region (semiconductor).
- junction width: determines the region over which the doping concentration gradually diffuses from the peak concentration (near the surface) to the lowest value (inside the semiconductor).
- distribution function: picks the analytic function used to describe the diffusion profile. The two options are Gaussian function and complementary error function.
- concentration: the peak concentration of dopants introduced at the surface.
- ref concentration: a low reference value for concentration that is used as the end point in the Gaussian or complementary error function profile.
Inside the diffusion doping object, the doping concentration goes from the (peak) concentration to the ref concentration over a distance equal to the junction width. This is illustrated in the following figure:
- The dark green face is the “mask-opening surface,” where the dopants were introduced. This can be placed on any of the faces by using the “source face” option.
- The green box represents the area where the doping concentration is at the peak value (“concentration”). Outside the box, the dopants start to diffuse into the material towards the outer faces of the large box (the diffusion doping object).
- The green box (the peak concentration area) ends from a certain distance away from all the faces of the large box. This distance is the “junction width.”
- The doping concentration goes from the peak value (“concentration”) to the “ref concentration” within this distance. This diffusion profile is modeled using an analytic function.
- The doping concentration at the faces of the large box (diffusion doping object) is thus equal to the “ref concentration” except for the surface where the dopants were introduced (the top surface here).