In aerospace applications, it is important to have efficient, small, affordable, and reliable power conversion units with high power density to supply a wide range of loads. Use of wide-band gap devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, in power electronic converters is expected to reduce the device losses and need for extensive thermal management systems in power converters, as well as facilitate high-frequency operation, thereby reducing the passive component sizes and increasing the power density. A performance comparison of state-of-the art power devices in a 10 kW full-bridge dc-dc buck converter operating in continuous conduction mode (CCM) and at switching frequencies above 100 kHz will be presented in this manuscript. Power devices under consideration are silicon (Si) IGBT with Si antiparallel diodes, Si IGBT with SiC antiparallel diodes, Si MOSFETs, SiC MOSFETs, and enhancement-mode GaN transistors. A 10 kW full-bridge dc-dc converter operating in the buck mode will be designed and tested using the LTSpice circuit simulator. Steady-state and switching transition waveforms will be presented for each case to aid the performance evaluation. From the simulation results, while the use of IGBTs resulted in efficiencies > 95 %, the switching frequency of commercially available devices is limited to 70 kHz, resulting in larger passive components and higher transients. Converter using Si devices exhibited slightly lower efficiencies than the one using SiC devices. SiC devices, rated at 1200 V, exhibited better transient response as well as switching transitions. Use of GaN devices resulted in efficiencies > 98%, thus yielding performance much superior to the others. However, the commercially available GaN devices can only withstand maximum voltage stresses 650 V.