Abstract: An electronic HEMT transistor structure comprises a heterojunction formed from a first layer, called a buffer layer, of a first wide bandgap semiconductor material, and a second layer of a second wide bandgap semiconductor material, with a bandgap width EG2 larger than that Eg1 of the first material, and a two-dimensional electron gas flowing in a channel confined in the first layer under the interface of the heterojunction. The first layer furthermore comprises a layer of a BGaN material under the channel, with an average boron concentration of at least 0.1%, improving the electrical performance of the transistor. Application to microwave power components.