Exploring the feasibility and conduction mechanisms of P-type nitrogen-doped β-Ga 2 O 3 with high hole mobility

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 10; no. 17; pp. 6673 - 6681
• Main Authors: Ma, Congcong, Wu, Zhengyuan, Jiang, Zhuoxun, Chen, Ying, Ruan, Wei, Zhang, Hao, Zhu, Heyuan, Zhang, Guoqi, Kang, Junyong, Zhang, Tong-Yi, Chu, Junhao, Fang, Zhilai
• Format: Journal Article
• Language: English
• Published: 05.05.2022
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D1TC05324H

P-type doping of ultrawide-bandgap semiconductors, which are the key materials for fabrication of next-generation high-performance optoelectronic and electronic devices, is extremely difficult to achieve. The lack of p-type Ga 2 O 3 has become a great obstacle to fabricate a full Ga 2 O 3 -based p–n homojunction for high-performance device applications. We demonstrate that N-doped β-Ga 2 O 3 achieved by a phase transition from GaN to β-Ga 2 O 3 possesses low formation energy and transition level ε (0/−), thereby with good N dopant solubility and low activation energy of N acceptors (0.355 eV). The delocalization effect, enhancement of valence band dispersion, and thus the decrease of the hole effective mass are predicted for N-doped β-Ga 2 O 3 due to the hybridization of O 2p with N 2p and Ga 4s orbitals. Activated hole concentrations of 6.1 × 10 15 and 2.1 × 10 16 cm −3 at a valence band maximum are predicted for β-Ga 2 O 3 :N O(III) obtained by the nonspin and spin-polarized calculations, respectively. The hole mobility is 1.3 cm 2 V −1 s −1 for undoped β-Ga 2 O 3 and remarkably increases to 8.8 and 5.5 cm 2 V −1 s −1 for β-Ga 2 O 3 :N O(III) obtained by the non-spin and spin-polarized calculations, respectively. The origins for the unusual increase of hole mobility are attributed to the decrease of the hole effective mass, and reduction in acoustic deformation potential scattering and optical phonon scattering due to the weakening of electron–phonon coupling by N-induced phonon stiffening for β-Ga 2 O 3 :N O(III) . The p-type conductivity of N-doped β-Ga 2 O 3 is demonstrated theoretically and also experimentally with a Hall hole concentration of 3.19 × 10 15 cm −3 and a Hall hole mobility of 23.1 cm 2 V −1 s −1 for N-doped β-Ga 2 O 3 films, and the p-type conductivity mechanisms are clarified. These studies will open a new horizon for other p-type wide bandgap oxide semiconductors.