Thermal stability of ALD-grown SiO2 and Al2O3 on (010) β-Ga2O3 substrates

Ultra-wide band gap semiconductors like β-Ga
2
O
3
undergo different high temperature processes during device fabrication. In addition, devices made with β-Ga
2
O
3
are also promising for high temperature applications. Therefore, it is very important to study thermal stability of materials and devices, as high temperatures are known to change the integrity of the dielectric and cause diffusion of atoms across different interfaces within the device. In this article, we study the thermal stability of SiO
2
and Al
2
O
3
formed using plasma-enhanced atomic layer deposition (PEALD) on (010) Sn-doped β-Ga
2
O
3
. Our study reveals that MOSCAPs made with SiO
2
maintains a breakdown strength (EBD) of > 10 MV/cm at temperatures up to 900 °C, while maintaining low leakage current at oxide electric fields E
ox
≤ 5 MV/cm. In comparison, devices made with Al
2
O
3
shows high leakage current (often starting at E
ox
~ 2.5 MV/cm) and interfacial/bulk crystallization (starting at 600°C). Interface trap density (NIT) probed using multi-frequency and UV-assisted C-V measurements shows ≤ 10
¹²
cm
²
for Al
2
O
3
and higher values for SiO
2
This is the first demonstration of better thermal stability for ALD SiO
2
compared to Al
2
O
3
formed on (010) β-Ga
2
O
3
substrates.