SCAPS-1D (http://scaps.elis.ugent.be/) is a tool that numerically solves the relevant equations based on a one-dimensional (layer) structure you define youself. It was intended for simulating band diagrams, IV characteristics, and capacitance spectroscopy measurements on solar cells, but works well for most structures you can think of. In my experience, it does not cope well with insulating structures if you go away from equilibrium, i.e. apply a voltage, but if you only need the band diagram under 0V, it works really well. You need to know fundamental physical properties of your materials, but pretty sure Si and SiO2 is predefined.
You can use OriginPro 2018 Graphing and analysis, is the butter for you to draw band bending at Si-SiO2 interfaces, but to show more information about the doping and annealing effects in the interface, you must overlay all the results on a single graph as a function of doping or annealing effects.