Doping and cluster formation in diamond

Abstract

Introducing a cluster formation model, we provide a rational fundamental viewpoint for the difficulty to achieve n-type doped diamond. We argue that codoping is the way forward to form appropriately doped shallow regions in diamond and other forms of carbon such as graphene. The electronegativities of the codopants are an important design criterion for the donor atom to efficiently donate its electron. We propose that the nearest neighbour codopants should be of a considerably higher electronegativity compared to the donor atom. Codoping strategies should focus on phosphorous for which there are a number of appropriate codopants.

On Enabling Nanocrystalline Diamond for Device Use: Novel Ion Beam Methodology and the Realization of Shallow N-Type Diamond

“…Where it was concluded by Yan et al that donor P is expectedly shallow (with ionization energy between 200 and 300 meV) where the solubility is believed to be enhanced near surface through the simultaneous inclusion of void-like planar defects and where the ionization energy may be distorted in the diamond volume through a DX-like distortion [7]. More recent theoretical modeling has concluded that by engineering the defect process through co-dopant introduction favorable changes may be made to the diamond electronegativity and could generate SD regions in the surrounding volume [10]. However, in both approaches the calculated formation energy is assumed to be strongly temperature dependent through the defect chemical potential, where…”

Electronegativity and doping in semiconductors

“…The high electronegativity of nitrogen as compared to carbon can explain its poor donor properties in diamond 16 as discussed in previous work. 10 Our findings have important implications for dopantdefect interactions. To surpass difficulties in the doping of semiconductors defect engineering strategies such as codoping are commonly used.…”

“…From these considerations, codoping strategies in diamond would benefit more if the donor atom was phosphorous for which there are numerous candidate codopants with higher electronegativities. 10 We have considered the doping of two isostructural host materials, silicon and diamond, which have significantly different electronegativities. For both materials, the results are qualitatively similar and depend on the differences of electronegativities with the dopants.…”

“…That is, an electron would transfer from the Si atoms (electronegativity 1.90) to the phosphorous atom (electronegativity 2.19) and from the Ga atom (electronegativity 1.81) to the Si atoms. The recently introduced cluster formation model 9,10 bridges the gap between the standard picture in semiconductors and electronegativities by considering that it is the cluster between the dopant atom and the nearest neighbor host atoms that donates (or accepts) the electron and not the isolated dopant. For example, if one considers an n-type dopant, such as P in Si, it does not donate an electron to the conduction band as commonly expected nor does it accept an charge as the electronegativities would dictate (P is more electronegative than Si).…”

Versatile Simple Doping Technique for Diamond by Solid Dopant Source Immersion during Microwave Plasma CVD

“…These unique functions of the devices originate mainly from the wide band gap and the ultra-hard lattice of diamonds, which create distinctive dopant states. Theoretical investigations predict that there are plenty of novel doped diamonds that have never been synthesized, such as n-type diamonds by co-doping of multiple elements 11,12 . Despite the long history of the doped diamonds 13 , it is worth pursuing the synthesis of novel doped diamonds.…”