Spontaneous polarization and polarization-induced electron sheet charge of YbAlN on GaN: A first-principles study
Spontaneous polarization and polarization-induced electron sheet charge of YbAlN on GaN: A first-principles study
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GaN 上 YbAlN 的自发极化和极化诱导电子片电荷：第一性原理研究
DOI：
10.1021/acsaelm.2c00995
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发表时间：
2022
影响因子：
4.7
通讯作者：
Morito Akiyama
中科院分区：
文献类型：
--
作者：
Kenji Hirata;Shoya Kawano;Hiroshi Yamada;Masato Uehara;Sri Ayu Anggraini;Morito Akiyama
掺钪AlN（ScAlN）中的高自发极化正被积极地研究用于各种电子器件。本研究通过第一性原理计算研究了掺镱AlN（YbxAl 1-xN）的自发极化。自发极化的幅度随着Yb浓度的增加而增加，并在x = 0.5时达到最大值-0.3 C/m2，这与ScAlN相当。此外，结果揭示了纤锌矿结构的晶格常数比（c/a）和自发极化之间的相关性。纤锌矿结构中Yb-N键沿着轴向的长度影响自发极化的大小。与Al-N键相比，Yb-N键更短，以及Yb与Al相比更高的Born有效电荷被认为是YbAlN高自发极化的主要因素。YbAlN/GaN异质结构中的极化诱导电子面电荷估计与ScAlN/GaN中的极化诱导电子面电荷相当。这些结果表明，YbAlN是一种很有前途的GaN基高电子迁移率晶体管的势垒层。在低Yb浓度下，YbxAl 1-xN和GaN缓冲层之间的晶格失配非常小。极化感应界面片电荷受自发极化和压电极化之和的影响。在YbAlN/GaN的情况下，压电极化被抑制到一个较低的水平，自发极化的影响增加，并导致更高的极化诱导界面片电荷。
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/m2atx= 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 thec-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.