First-Principles Calculations of P-B Co-Doped Cluster N-Type Diamond

At a Glance

Metadata	Details
Publication Date	2024-05-16
Journal	Crystals
Authors	Huaqing Lan, Sheng Yang, Wen Yang, Maoyun Di, Hongxing Wang
Institutions	Taiyuan University of Science and Technology, Xi’an Jiaotong University
Citations	2
Analysis	Full AI Review Included

Executive Summary

This study utilizes first-principles calculations (DFT-HSE06) to investigate stable, low-ionization-energy n-type doping in diamond using Phosphorus (P) and Boron (B) co-doping strategies.

P-Doping Instability: Isolated substitutional P doping (C₂₁₅P₁) is highly unstable, exhibiting an excessive formation energy of 7.493 eV and significant lattice distortion.
P-V Complex Limitation: The P-Vacancy (P-V) complex (C₂₁₄P₁V₀) is more stable (5.702 eV) but unexpectedly functions as a P-type semiconductor, rendering it unsuitable for n-type device fabrication.
Cluster Stabilization: Introducing Boron (B) as a compensatory dopant significantly improves P solubility and stability, promoting the formation of P-B cluster states (e.g., P-P-B, P-B-P).
Optimal N-Type Performance: The P-B-P cluster configuration achieved the lowest calculated donor ionization energy (1.52 eV), demonstrating superior n-type characteristics compared to other configurations.
Mechanism of Improvement: The formation of aggregated cluster states effectively reduces the ionization energy and mitigates the severe lattice distortion caused by isolated P atoms, enhancing electron mobility.
B Compensation Role: B atoms primarily act as stabilizers and compensators; the donor energy level is predominantly determined by the P atoms within the cluster structure.

Technical Specifications

The following data points were extracted from the first-principles calculations, focusing on stability (Formation Energy) and electrical performance (Ionization Energy).

Parameter	Value	Unit	Context
Pure Diamond Band Gap (HSE06)	5.381	eV	Calculated value, validating method against experimental 5.480 eV.
P Substitution (C₂₁₅P₁) Formation Energy	7.493	eV	High energy, indicating poor solubility.
P-Vacancy (C₂₁₄P₁V₀) Formation Energy	5.702	eV	More stable than P substitution, but yields P-type semiconductor.
P-P-P Cluster (C₂₁₃P₃) Formation Energy	25.35	eV	Highly unstable cluster configuration.
Optimal P-P-B Cluster Formation Energy	10.32	eV	Lowest formation energy among P-B co-doped clusters.
Optimal Ionization Energy (P-B-P)	1.52	eV	Lowest donor level achieved, critical for n-type conductivity.
P-P-B Ionization Energy	1.68	eV	Second lowest donor level.
P-C-P-C-B Ionization Energy	2.45	eV	Highest ionization energy (atoms separated by C atoms).
P Doping Lattice Constant (Avg.)	10.752	Angstrom	High lattice distortion (C₂₁₅P₁).
P-V Doping Lattice Constant (Avg.)	10.718	Angstrom	Reduced lattice distortion (C₂₁₄P₁V₀).

Key Methodologies

The study employed advanced Density Functional Theory (DFT) simulations to model and analyze the electronic and structural properties of doped diamond.

Simulation Package: The Density Functional Theory-based Sequential Total Energy Package (CASTEP) was utilized for all structural optimizations and property calculations.
Structural Optimization: The Generalized Gradient Approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) functional was employed for modeling atomic relaxation and exchange-correlation energy.
Electronic Property Calculation: The Heyd-Scuseria-Ernzerhof (HSE) 06 hybrid functional was selected for calculating the band structure, density of states (DOS), and ionization energy due to its accuracy in predicting the diamond band gap (5.381 eV).
Supercell Model: A periodic supercell containing 216 atoms (3 x 3 x 3 configuration) was used to model the pristine and doped diamond structures.
Energy Cutoff: A fixed plane-wave energy cutoff of 750 eV was maintained across all computational procedures.
Convergence Criteria: Geometric optimization required residual forces acting on individual atoms to be less than 10^-3 eV/Angstrom. Self-consistent field (SCF) energy convergence was set to 1.0 x 10^-5 eV/atom.
Impurity Analysis: Formation energy calculations incorporated chemical potentials derived from hybrid calculations of P₂H₆ and BH₃ in the gas phase, along with electrostatic potential correction factors (ΔE).

Commercial Applications

The successful theoretical demonstration of stable, low-ionization-energy n-type diamond doping opens pathways for next-generation semiconductor devices leveraging diamond’s extreme properties.

High-Power Switching Devices: Enabling the fabrication of diamond p-n junctions and n-type layers for high-voltage (HV) and ultra-high-voltage (UHV) power electronics, such as rectifiers and MOSFETs, due to diamond’s high breakdown voltage and thermal conductivity.
High-Frequency Electronics: Development of high-speed, high-frequency devices (e.g., RF amplifiers and HEMTs) that benefit from diamond’s high carrier mobility and ability to dissipate heat efficiently.
Extreme Environment Sensors: Utilization in sensors and electronic components designed for harsh conditions, including high temperatures (greater than 500 K) and high radiation fields, where conventional silicon or SiC devices degrade.
Deep UV Optoelectronics: Creation of n-type contacts and active layers for deep ultraviolet (DUV) light-emitting diodes (LEDs) and photodetectors, leveraging the wide bandgap.
Thermal Management Substrates: Integration of doped diamond layers into electronic packaging to serve as highly efficient heat spreaders for high-density integrated circuits.

View Original Abstract

To achieve n-type doping in diamond, extensive investigations employing first principles have been conducted on various models of phosphorus doping and boron-phosphorus co-doping. The primary focus of this study is to comprehensively analyze the formation energy, band structure, density of states, and ionization energy of these structures. It is observed that within a diamond structure solely composed of phosphorus atoms, the formation energy of an individual carbon atom is excessively high. However, the P-V complex substitutes 2 of the 216 carbon atoms, leading to the transformation of diamond from an insulator to a p-type semiconductor. Upon examining the P-B co-doped structure, it is revealed that the doped impurities exhibit a tendency to form more stable cluster configurations. As the separation between the individually doped atoms and the cluster impurity structure increases, the overall stability of the structure diminishes, consequently resulting in an elevation of the ionization energy. Examination of the electronic density of states indicates that the contribution of B atoms to the impurity level is negligible in the case of P-B doping.

Tech Support

Original Source

DOI: https://doi.org/10.3390/cryst14050467

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