Schottky-Contact Technology in InAlN/GaN HEMTs for Breakdown Voltage Improvement

In this paper, we demonstrate a 253% improvement in the off-state breakdown voltage (BV) of the lattice-matched In_0.17Al_0.83 N/GaN high-electron-mobility transistors (HEMTs) by using a new Schottky-contact technology. Based on this concept, the Schottky-source/drain and Schottky-source (SS) InAlN/GaN HEMTs are proposed. The proposed InAlN/GaN HEMTs with an L_GD of 15 μm showed a three-terminal BV of more than 600 V, while the conventional InAlN/GaN HEMTs of the same geometry showed a maximum BV of 184 V. Without using any field plate, the BV of 650 V was measured in the SS InAlN/GaN HEMTs with L_GD = 15 μm, which is the highest BV ever achieved on InAlN/GaN HEMT. The corresponding specific on-resistance (R_sp, _on) is as low as 3.4 mΩ·cm². A BV of 118 V was also obtained in SS InAlN/GaN HEMTs with L_GD = 1 μm, which is the highest BV in GaN-based HEMTs featuring such a short L_GD with GaN buffer. The improvement of the BV relies on the effective suppression of source carrier injection into the GaN buffer under the SS due to the smooth metal morphology and elimination of metal spikes in the Schottky metallization.