Enhancement-Mode AlGaN/AlN/GaN High Electron Mobility Transistor with Low On-State Resistance and High Breakdown Voltage

A low on-resistance and high-breakdown-voltage enhancement-mode (E-mode) AlGaN/AlN/GaN high electron mobility transistor (HEMT) was fabricated without the recessed-gate process. A thin AlGaN barrier layer (4.5 nm) was used for the normally-off operation. In order to decrease the on-state resistance, two different techniques are used. One is the side-ohmic contact, which has a low contact resistance, due to the direct contact with the two-dimensional electron gas (2DEG). The other is SiO2 passivation, which induces the sheet carriers and decreases the sheet resistance. As a result, an on-state resistance of 1.9 mΩ·cm2 and an off-state breakdown voltage of 610 V were achieved for the E-mode HEMT within a threshold voltage of approximately -0.1 V.