This work examines particularities in the switching characteristics of gallium nitride (GaN) half-bridge and driver circuits, which arise from the integration on a common conductive silicon (Si) substrate. The supposed advantages of monolithic integrated half-bridges and drivers are promising: The reduced parasitic interconnect inductance improves voltage-switching transitions. The Si carrier allows low-cost and large-scale fabrication. A single integrated IC simplifies the assembly compared to conventional multi-chip power modules. However, the operation of such integrated GaN-on-Si power circuits also evokes substrate-related effects, which were previously not relevant for discrete low-side GaN HEMTs. The experimental and theoretical investigation of this work on the switching characteristic of GaN-on-Si half-bridges with drivers on conductive Si substrates contributes to unlock the benefits of GaN HEMTs and monolithic power circuit integration for compact, clean switching and highly efficient power electronics.