Highly Reliable GaN-MOSFETs with High Channel Mobility Gate by Selective-Area Crystallization

We realized the high reliability of normally-off GaN MOSFETs with high mobility SiO
2
/AlN/GaN stacked gate formed by newly selective-area crystallization using atomic layer deposition (ALD) method. By using this technique, the single crystalline AlN layer and amorphous AlN layer are selectively deposited in the gate region and in the access region, respectively. By introducing the single crystalline AlN into the SiO
2
/GaN interface, the channel mobility is enhanced from 105 to 490 cm
²
/Vs. In addition, the GaN MOSFETs also have superior long-term reliability with regard to time-dependent dielectric breakdown (TDDB) and high-temperature reverse bias (HTRB). In particular, expected HTRB lifetime of 0.1% failure under the drain voltage of 650 V is over 10 years, which is comparable to that of normally-on GaN FETs and normally-off GaN JFETs. These results show that the GaN MOSFETs with high mobility gate-recessed SiO
2
/AlN/GaN structure formed by selective-area crystallization technique are promising for practical power applications.