Journal
ACS APPLIED ELECTRONIC MATERIALS
Volume -, Issue -, Pages -Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsaelm.2c00995
Keywords
first-principles calculation; spontaneous polarization; piezoelectricity; high-electron-mobility transistors; nitrides
Funding
- Japan Society for the Promotion of Science (JSPS KAKENHI) [21K14503, 22H01784]
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This study investigated the spontaneous polarization of ytterbium-doped aluminum nitride and its correlation with the lattice-constant ratio of the wurtzite structure. The results suggest that YbAlN is a promising barrier layer for GaN-based high-electron-mobility transistors.
The high spontaneous polarization in scandium-doped AlN (ScAlN) is being actively investigated for applications to various electronic devices. In this study, spontaneous polarization of ytterbium-doped AlN (YbxAl1-xN) was investigated by first-principles calculations. The magnitude of spontaneous polarization increases with increasing Yb concentration and reaches the maximum value of -0.3 C/m(2) at x = 0.5, which is comparable with that of ScAlN. Moreover, the results revealed the correlation between the lattice-constant ratio (c/a) of the wurtzite structure and spontaneous polarization. The value of spontaneous polarization is affected by the length of the Yb-N bonds along the c-axis in the wurtzite structure. The shorter Yb-N bonds compared with Al-N bonds and higher Born effective charge of Yb compared with Al are considered to be the main factors for the high spontaneous polarization of YbAlN. The polarization-induced electron sheet charge in YbAlN/GaN heterostructures is estimated to be comparable with that in ScAlN/GaN. These results suggest that YbAlN is a promising barrier layer for GaN-based high-electron-mobility transistors. At low Yb concentration, the lattice mismatch between YbxAl1-xN and the GaN buffer layer is very small. The polarization-induced interface sheet charge is affected by the sum of the spontaneous and piezoelectric polarization. In the case of YbAlN/GaN, the piezoelectric polarization is suppressed to a low level, and the effect of spontaneous polarization increases and leads to higher polarization-induced interface sheet charge.
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