This paper presents the design, analysis, fabrication and experimental results of a synchronous DC-DC converter using Gallium Nitride (GaN) switching devices at 500 kHz. An efficiency of above 97% has been achieved even while switching at 500 kHz. A GaN half-bridge circuit board has been designed for fabrication of a general purpose inverter in the laboratory. The circuit is operated in synchronous buck mode to test the switching performance and power handling capability at higher frequencies. The thermal management of a GaN device is essential and is duly taken care of. A thermal modelling of the devices along with the heat-sink is also presented here. A comparative study is then presented with an existing SiC based converter for 200 kHz operation in terms of loss, efficiency, temperature rise etc. This work is expected to help potential researchers in this field to develop advanced and compact power converter boards.