Recent advancement of GaN HEMT with InAlGaN barrier layer and future prospects of A1N-based electron devices

The high-power operation of InAlGaN/GaN high-electron-mobility transistor (HEMT) amplifiers in the wide-frequency range from the S-band to the W-band has been achieved. A re-grown n + -GaN contact layer and an InGaN back-barrier layer was employed for the W-band GaN HEMT amplifiers. For the S-band, 2-dimensional electron gases (2DEG) mobility was improved using atomically flat AlGaN spacer layers. This technology allows us to reduce the 2DEG densities maintaining the low access resistance, which contributes to the lower electric-field concentration at the edge of gate electrodes i.e. enables high voltage operation. Furthermore, a diamond heat spreader was introduced to decrease the thermal resistance and we successfully confirmed the further improvement in the output power density. Finally, AlN-based next generation devices are proposed and the lower thermal resistance are expected compared to the conventional GaN/SiC structures.