Regulating the valence level arrangement of high-Al-content AlGaN quantum wells using additional potentials with Mg doping

Shiqiang Lu; Tongchang Zheng; Ke Jiang; Xiaojuan Sun; Dabing Li; Hangyang Chen; Jinchai Li; Yinghui Zhou; Duanjun Cai; Shuping Li; Wei Lin; Junyong Kang

doi:10.1039/d1cp04303j

Regulating the valence level arrangement of high-Al-content AlGaN quantum wells using additional potentials with Mg doping

Phys Chem Chem Phys. 2022 Mar 2;24(9):5529-5538. doi: 10.1039/d1cp04303j.

Authors

Affiliations

¹ Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, Department of Physics, Xiamen University, Xiamen 361005, China. linwei@xmu.edu.cn.
² Department of Physics, School of Science, Jimei University, Xiamen 361021, China.
³ State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Dongnanhu Road No. 3888, Changchun 130033, China.

PMID: 35172325
DOI: 10.1039/d1cp04303j

Abstract

Quantum states and arrangement of valence levels determine most of the electronic and optical properties of semiconductors. Since the crystal field split-off hole (CH) band is the top valence band in high-Al-content AlGaN, TM-polarized optical anisotropy has become the limiting factor for efficient deep-ultraviolet (DUV) light emission. Additional potentials, including on-site Coulomb interaction and orbital state coupling induced by magnesium (Mg) doping, are proposed in this work to regulate the valence level arrangement of AlN/Al_0.75Ga_0.25N quantum wells (QWs). Diverse responses of valence quantum states |p_i〉 (i = x, y, or z) of AlGaN to additional potentials due to different configurations and interactions of orbitals revealed by first-principles simulations are understood in terms of the linear combination of atomic orbital states. A positive charge and large Mg dopant in QWs introduce an additional Coulomb potential and modulate the orbital coupling distance. For the CH band (p_z orbital), the Mg-induced Coulomb potential compensates the orbital coupling energy. Meanwhile, the heavy/light hole (HH/LH) bands (p_x and p_y orbitals) are elevated by the Mg-induced Coulomb potential. Consequently, HH/LH energy levels are relatively shifted upward and replace the CH level to be the top of the valence band. The inversion of optical anisotropy and enhancement of TE-polarized emission are further confirmed experimentally via spectroscopic ellipsometry.