Title:	Lattice sites of dopants in transition metal ion implanted GaN
DNr:	SNIC 2019/7-91
Project Type:	SNIC Small Compute
Principal Investigator:	Sanjay Kumar Nayak <sanjay.kumar.nayak@liu.se>
Affiliation:	Linköpings universitet
Duration:	2019-12-01 – 2020-12-01
Classification:	10304
Keywords:

Abstract

In a dilute magnetic semiconductor (DMS), magnetic atoms (or impurities) are introduced in an otherwise non-magnetic semiconductor. The co-existence of ferromagnetism and semiconducting behaviour in some DMS materials has generated fundamental new physics and enabled the study of phenomena of interest for spintronics where both charge and spin properties of the electron can be simultaneously used for both data processing and storage in development of highspeed computation. The main challenge for the practical realization of the spintronics based devices is the DMS with a high Curie temperature (Tc), preferably above room temperature (RT). However, for many reasons such as lattice defects and different charge states of dopants in host, most of the DMS possess a low Tc. Manganese (Mn) doped GaAs has been the “Drosophila” for the study of spintronics in III-V semiconductors. Currently, the highest reported Tc of GaAs:Mn is ~ 183 K [Phys. Rev. B 93, 184417 (2016), Phys. Rev. Materials 1, 054401 (2017), Appl. Phys. Lett. 93, 132103 (2008)] much below the room temperature (RT), partly because that Mn occupies both substitutional and interstitial sites. Dietl et al. [Science 287,1019 (2000)] showed that the Tc of Mn-doped GaN is ~ 400 K which shows a great promise in the development of spintronics devices. However, Mn at 3+ charge states shows very low Tc whereas at 2+ states the nearest neighbour interaction is antiferromagnetic. Thus, various other 3d transitions metals ions are being used as dopant to GaN for exploration of GaN-based DMS with high Tc. It is to note that the magnetization and Tc are strongly depended upon the growth or synthesis conditions [Phys. Stat. Sol. (A) 204, No. 1, 61–71 (2007)] which control the dynamics of dopants and finally determines the lattice sites in host. Since transition metals have multiple valence states, growth conditions can influence the stability of charge states of the dopants and consequently the magnetic interaction between them. Growth condition further influence the lattice defect concentrations which can compensate the magnetic moment caused by magnetic dopants in host [Phys. Rev. B 84, 035206 (2011), Phys. Rev. B 81, 184425 (2010)]. Identification of these defect using experimental technique is a nearly impossible task and thus studies based on first principles are must for better understanding. In this work, we investigate the formation energies and stability of various point defects in Co, Fe, Mn and Ni-doped wurtzite GaN using First-principles DFT simulations. Further our results will be validated with the experimental data obtained with the experimental data recorded with emission channelling (EC) technique.