A series of heterostructure designs of low-voltage InP homothyristors have been investigated using numerical simulation methods. The design with a space charge layer formed in the p-base region of the n-p-n transistor part was considered as the base one. The dynamic characteristics and processes that determine the rate of transition to the on state are investigated. It is shown that as the p-base thickness increases from 1 to 2.6 μm, the maximum on-state currents increase from 70 to 90 A, while the minimum turn-on transition time is 11 ns at a maximum blocking voltage of 55 V. It is shown that the operation efficiency in the on state is determined by the residual voltage. Residual voltage decreases with a decrease in the thickness of the p-base.