A novel AlGaN/GaN high electron mobility transistors with the partial fixed positive charge in buffer layer

For the special breakdown mechanism of AlGaN/GaN HEMTs devices, a novel AlGaN/GaN HEMTs with the partial fixed positive charge in buffer layer is proposed in this paper. Through the introduction of the partial fixed positive charge in buffer layer, 2DEG in the area is depleted, then the low 2DEG density region is formed, which modulate the concentration of 2DEG and the surface electric field distribution of the AlGaN/GaN heterojunction. The high electric field peak at the gate edge is decreased effectively, due to the new electric field peak introduced by the partial fixed positive charge, therefore the surface electric field distribution becomes more uniform, the breakdown voltage is improved from 97.5V for the conventional structure to 195V for the single LDD(when injected into a single positive charge) and 285V for the double LDD(when injected into two different amounts of positive charges), respectively. Because of the auxiliary depletion effect of partial fixed positive charge, the concentration of 2DEG decreases. So the output current of AlGaN/GaN HEMTs reduces by 10%( single LDD) and 25%( double LDD), respectively. This is the compromision of improving the breakdown voltage.