In this article, the volt-ampere characteristic of p–n junction diodes under the influence of a magnetic field and the change in the volume charge field parameters were theoretically studied. That is, the effect of the electromotive force (EMF), the Lorentz force, and the change in the distribution of charge carriers generated under the influence of a magnetic field on the width of the volume charge field, diffusion current, diffusion capacitance, and volume capacitance of the p–n junction was analyzed based on a mathematical model. The calculation results showed that the mobility of charge carriers increased under the influence of a temperature gradient, and the Lorentz force changed their direction and spatial distribution under the influence of a magnetic field, resulting in a change in the diffusion and volume capacitances depending on the magnetic induction. Also, these processes were analyzed comparatively for homogeneous and heterogeneous semiconductors, and the importance of the magnetic field in controlling the electrical parameters of p–n junction diodes was theoretically substantiated.