Density functional theory calculations of stability and diffusion mechanisms of impurity atoms in Ge crystals

Abstract

Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites of 2nd to 6th row element impurity atoms in Ge crystal were undertaken with density functional theory (DFT) and compared with those in Si crystal. It was found that most of the impurity atoms in Ge were stable at substitutional sites, while transition metals in Si were stable at interstitial sites and the other impurity atoms in Si were stable at substitutional sites. Furthermore, DFT calculations were carried out to clarify the mechanism responsible for the diffusion of impurity atoms in Ge crystals. The diffusion mechanism for 3d transition metals in Ge was found to be an interstitial-substitutional diffusion mechanism, while in Si this was an interstitial diffusion mechanism. The diffusion barriers in the proposed diffusion mechanisms in Ge and Si were quantitatively verified by comparing them to the experimental values in the literature.

Diffusion and Dopant Activation in Germanium: Insights from Recent Experimental and Theoretical Results

“…Obviously, no review can consider all the references related to such a technological issue and many key contributions have not been discussed (for example, References [114][115][116][117][118][119][120]). Additionally, from an experimental viewpoint, the diffusion and activation of dopants can be further complicated by parameters such as the thermal budget, particularly when considering non-equilibrium techniques (e.g., laser, flash, and microwave annealing) [121,122].…”

High-Throughput Screening of Extrinsic Point Defect Properties in Si and Ge: Database and Applications

“…Such sites are indeed experimentally observed for O and N. , When the latter lower-symmetry sites are explicitly simulated, both elements strongly prefer an interstitial site, twofold-coordinated for O and trifold-coordinated for N, as well as a distorted substitutional site. Maeta and Sueoka examined the twofold-coordinated site for larger elements also but found that it quickly becomes enthalpically unfavorable . The remaining TV positions in Ge consist of transition metals, which are capable of increased interactions through their incomplete d shells.…”

“…While Si has been the focus of the semiconductor industry for the last 50 years, Ge has recently regained interest as a high-mobility substrate and is still commonly used in niche markets such as radiation detectors and space solar cells. − Impurities are essential to both materials, providing control over the semiconductor’s properties during production and device operation. Knowledge of impurity properties in Ge is significantly less complete than for Si, and even for the latter only a subset of the periodic table has been studied. ,− Through high-throughput screening this knowledge can be considerably extended beyond what is currently experimentally known. In this way a complete and consistent data set can be provided for both materials and used to gain insights into future experimental and theoretical research as well as industrial applications.…”

Probing the Local Atomic Structure of In and Cu in Sphalerite by XAS Spectroscopy Enhanced by Reverse Monte Carlo Algorithm

“…The formation energies of sphalerite solid solutions (E FE , [12,14]) were obtained using the calculated total energies. We considered the following models: two In atoms substitute for two Zn atoms in ZnS crystal structure; two In atoms substitute for two Zn atoms in ZnS crystal structure with the formation of a vacancy at Zn position; one In and one Cu atom substitute for two Zn atoms in ZnS crystal structure.…”