Improved breakdown voltage of AlGaN/GaN HEMTs grown on Si substrates using partially Mg-doped GaN buffer layer by MOCVD

Abstract

AlGaN/GaN high electron mobility transistors (HEMTs) were grown on Si substrates by MOCVD. In the HEMT structure, a 1 μm GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer leakage. The AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg doping. For the device with the partially Mg-doped GaN buffer layer, a lower drain leakage current density of 55.8 nA/mm, a lower gate leakage current density of 2.73 μA/mm, and a higher off-state breakdown voltage of 104 V were achieved with device dimensions Lg/Wg/Lgs/Lgd=1/10/1/1 μm, better than the device with the undoped GaN buffer layer, which has a higher drain leakage current density of 9.2 μA/mm, a higher gate leakage current density of 91.8 μA/mm, and a lower off-state breakdown voltage of 87 V with the same device dimensions.