The AlN lattice-polarity inversion in a high-temperature-annealed c-oriented AlN/sapphire originated from the diffusion of Al and O atoms from sapphire

Ke Jiang; Jianwei Ben; Xiaojuan Sun; Zhiming Shi; Xianjun Wang; Tong Fang; Shanli Zhang; Shunpeng Lv; Yang Chen; Yuping Jia; Hang Zang; Mingrui Liu; Dabing Li

doi:10.1039/d3na00780d

The AlN lattice-polarity inversion in a high-temperature-annealed c-oriented AlN/sapphire originated from the diffusion of Al and O atoms from sapphire

Nanoscale Adv. 2023 Nov 20;6(2):418-427. doi: 10.1039/d3na00780d. eCollection 2024 Jan 16.

Authors

Ke Jiang^{1

2}, Jianwei Ben^{1

2}, Xiaojuan Sun^{1

2}, Zhiming Shi^{1

2}, Xianjun Wang^{1

2}, Tong Fang^{1

2}, Shanli Zhang^{1

2}, Shunpeng Lv^{1

2}, Yang Chen^{1

2}, Yuping Jia^{1

2}, Hang Zang^{1

2}, Mingrui Liu^{1

2}, Dabing Li^{1

2}

Affiliations

¹ State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences Changchun 130033 P. R. China sunxj@ciomp.ac.cn lidb@ciomp.ac.cn.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences Beijing 100049 P. R. China.

Abstract

AlN films are widely used owing to their superior characteristics, including an ultra-wide bandgap, high breakdown field, and radiation resistance. High-temperature annealing (HTA) makes it easy to obtain high-quality AlN films, with the advantages of a simple process, good repeatability, and low cost. However, it is always found that there is a lattice-polarity inversion from a N-polarity near the sapphire to an Al-polarity in the HTA c-oriented AlN/sapphire. Currently, the formation mechanism is still unclear, which hinders its further wide applications. Therefore, the formation mechanism of the polarity inversion and its impacts on the quality and stress profile of the upper AlN in the HTA c-oriented AlN/sapphire were investigated. The results imply that the inversion originated from the diffusion of the Al and O atoms from the sapphire. Due to the presence of abundant Al vacancies (V_Al) in the upper AlN, Al atoms in the sapphire diffuse into the upper AlN during the annealing to fill the V_Al, resulting in the O-terminated sapphire, leading to the N-polar AlN. Meanwhile, O atoms in the sapphire also diffuse into the upper AlN during the annealing, forming an Al_xO_yN_z layer and causing the inversion from N- to Al-polarity. The inversion has insignificant impacts on the quality and stress distribution of the upper AlN. Besides, this study predicts the presence of a two-dimensional electron gas at the inversion interface. However, the measured electron concentration is much lower than that predicted, which may be due to the defect compensation, low polarization level, and strong impurity scattering.