This article presents the results of simulation the heterostructure of normally-off p-channel transistor. The design of the upper layers of the heterostructure was determined to induce the appearance of a 2DHG at the p-GaN/AlGaN heterojunction. By studying the band diagrams, the dependence of the transistor behavior on the thickness of the p-GaN and the impurity concentration within it is demonstrated for the p-channel device. Additionally, through analysis of the current-voltage characteristics the relationship between the formation of a normally-on or normally-off transistor and the thickness of the p-GaN layer, as well as the impurity concentration within it, was determined.