A field effect transistor configured for use in high power applications and a method for its fabrication is disclosed. The field effect transistor is formed of III-V materials and is configured to have a breakdown voltage that is advantageous for high power applications. The field effect transistor is so configured by determining the operating voltage and the desired breakdown voltage for that operating voltage. A peak electric field is then identified that is associated with the operating voltage and desired breakdown voltage. The device is then configured to exhibit the identified peak electric field at that operating voltage. The device is so configured by selecting device features that control the electrical potential in the device drift region is achieved. These features include the use of an overlapping gate or field plate in conjunction with a barrier layer overlying the device channel, or a p-type pocket formed in a region of single-crystal III-V material formed under the device channel. The overlapping gate/field plate or p-type pocket extend into the drift region of the device, controlling the electrical potential of the device in a manner that provides the desired control of the electrical potential in the drift region.