Stabilizing the defect-induced dilute magnetic semiconductors: Li-doping in GaN with Ga vacancies

¹ Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University - Box 530, S-751 21 Uppsala, Sweden, EU
² Laboratory for Quantum Engineering and Micro-Nano Energy Technology, Faculty of Materials, Optoelectronics and Physics, Xiangtan University - 411105, Hunan, China
³ Quantum Functional Semiconductor Research Center (QSRC), Dongguk University - 26 Phildong 3ga, Chung gu, Seoul 100-715, Korea
⁴ Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH) - S-100 44 Stockholm, Sweden, EU

^a jawad.nisar@fysik.uu.se
^b xiangyang.peng@fysik.uu.se

Received: 14 November 2010
Accepted: 9 February 2011

Abstract

By means of first-principles calculations, we have investigated the effects of various Li-doping on the exchange interaction and the formation energy in bulk GaN with Ga vacancies. Although the Ga vacancies can induce ferromagnetism in GaN, their formation energy is rather high. Our calculations show that Li-doping can effectively tune the formation energy of Ga vacancies. It is revealed that the stabilizing effect depends on whether the number of holes is increased or decreased after Li-doping. When Li atoms substitutes for N atoms or occupies the interstitial sites, the holes are reduced and the formation energy of Ga vacancies is lowered. In contrast, Li substituting for Ga generates additional holes in the system, leading to an enhancement of the formation energy of Ga vacancies and making the system less stable.