Abstract: The width of the depletion region is a fundamental parameter of PN junctions. In solid state physics textbooks, the calculation of depletion widths is usually limited to materials such as Si and Ge, and there is a lack of analysis of the PN junction of the wide bandgap semiconductor material likeGaN. The width of the depletion region is closely related to the charge density of the depletion region. The ionization energies of donors and acceptors in Si and Ge materials are relatively low, allowing for complete ionization at room temperature. Thus, the charge density in the depletion region is obviously equal to the impurity concentration. In contrast, the ionization energy of the acceptor dopant Mg in pGaN is approximately 220 to 270 meV, resulting in only part of Mg impurities undergoing ionization at room temperature. Therefore, the width of the GaN PN junction depletion region will be determined by both the impurity concentration and the degree of ionization. In this paper, the degree of ionization of different impurities in GaN material under different concentrations is calculated. The results show that the degree of Mg ionization is indeed very low when pGaN is heavily doped to 1019 cm-3in order to obtain sufficient hole concentration.Subsequently, using an opensource solver based on the ScharfetterGummel method to solve the driftdiffusion equations, we simulate the GaN PN junction and calculate important parameters such as depletion region width and impurity ionization levels. According to the simulation results, the impurity ionization level in the GaN PN junctions depletion region is significantly enhanced. Therefore, the width of the depletion region of the GaN PN junction can be appropriately calculated with the doping concentration. The research in this paper supplements the content of GaN PN junction in the textbook of solidstate physics, which is helpful for the study of subsequent courses.

Key words: GaN, ionization of impurity, PN junctions, depletion region width