Effect of various Fe-doped AlGaN buffer layer of AlGaN/GaN HEMTs on Si substrate

Abstract

AlGaN/GaN high-electron mobility transistors (HEMTs) with different Fe-doped Al0.25Ga0.75N buffer layers were fabricated on silicon (Si) substrate to improve breakdown voltage and reduce leakage current. Fe doping concentrations for the AlGaN buffer layers were designed as 5 × 1017, 6 × 1017, 7 × 1017, and 8 × 1017 cm−3. The fabricated HEMT with the Fe-doped concentration of 8 × 1017 cm−3 achieved a lower gate leakage current of 8.22 × 10−6 mA/mm, higher breakdown voltage (VBR) of −193 V, and higher buffer breakdown voltage (VBR_buffer) of −1324 V than did other devices with different doping concentrations. In addition, a slight decline in drain current dispersion in pulsed measurements and a slight increase in noise were obtained for HEMTs with a more Fe-doped buffer layer, because the increased Fe-doped concentration resulted in the formation of more buffer traps. However, these results suggest that the HEMT with a highly resistant AlGaN buffer layer of doped Fe has great potential for high-power integrated circuit applications.