Modulation of Diamond PN Junction Diode with Double-Layered n-Type Diamond by Using TCAD Simulation

At a Glance

Metadata	Details
Publication Date	2024-04-28
Journal	Electronics
Authors	Caoyuan Mu, Genzhuang Li, Xianyi Lv, Qiliang Wang, Hongdong Li
Institutions	Jilin University
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond PN Junction Diode Modulation

Source Paper: Modulation of Diamond PN Junction Diode with Double-Layered n-Type Diamond by Using TCAD Simulation (Electronics 2024, 13, 1703)

Executive Summary

This technical analysis summarizes the key findings of a TCAD simulation study proposing a novel vertical diamond PN Junction Diode (PND) structure utilizing a double-layered n-type diamond Junction Termination Extension (JTE).

Core Innovation: Introduction of a double-layer n⁺/n^- diamond JTE structure (D-PND) to effectively manage electric field crowding at the PN junction interface.
Performance Metric: The D-PND structure achieved a maximum Baliga’s Figure of Merit (BFOM = V_bd² / R_on) of 0.42 GW/cm².
Key Achievement: This BFOM represents a significant 12x improvement over the worst-case single-layer PND (S-PND) simulation (0.03 GW/cm²) and a 35% improvement over the best S-PND result (0.31 GW/cm²).
Optimal Parameters: Best performance was achieved with a 100 nm n^- layer (5 x 10¹⁷ cm^-3) and a 50 nm n⁺ layer (1 x 10¹⁸ cm^-3), demonstrating the necessity of precise, thin-layer doping control.
Application Relevance: The results confirm the potential of vertical diamond PNDs for high-power, high-efficiency power electronics applications requiring superior breakdown voltage (V_bd) and low on-resistance (R_on).
Material Challenge Addressed: The double-layer design mitigates the challenges associated with achieving high-quality, highly doped n-type diamond, which is critical for industrialization.

Technical Specifications

The following table summarizes the optimal simulated electrical performance and critical structural parameters of the Double-Layered PND (D-PND).

Parameter	Value	Unit	Context
Maximum BFOM	0.42	GW/cm²	Achieved by D-PND (S₁ = 1 µm)
Breakdown Voltage (V_bd)	1450	V	Optimal D-PND performance
On-Resistance (R_on)	5.08	mΩ·cm²	Optimal D-PND performance
Turn-On Voltage (V_on)	5.7	V	Consistent across S-PND simulations
Critical Electric Field (E_crit)	6	MV/cm	Set for diamond impact ionization model
Operating Temperature (T)	550 (277)	K (°C)	Suitable temperature for dopant activation
p⁺ Substrate Thickness	1	µm	Heavily doped region
p^- Drift Layer Thickness	4	µm	Lightly doped region
n^- Layer Thickness (D₁)	100	nm	Optimal thickness for low doping
n⁺ Layer Thickness (D₂)	50	nm	Optimal thickness for high doping
p⁺ Hole Concentration	1 x 10¹⁹	cm^-3	Substrate doping concentration
p^- Hole Concentration	1 x 10¹⁶	cm^-3	Drift region doping concentration
n⁺ Electron Concentration	1 x 10¹⁸	cm^-3	High doping layer (D₂)
n^- Electron Concentration	5 x 10¹⁷	cm^-3	Low doping layer (D₁)

Key Methodologies

The research utilized Silvaco TCAD software (Version 5.0.10.R) to simulate the vertical diamond PND structures (S-PND and D-PND). The methodology focused on accurately modeling charge transport and recombination phenomena in wide bandgap diamond.

Device Structure Definition:
- Vertical PND structure defined with p⁺ (anode contact), p^- (drift region), and n-type layers (cathode contact/JTE).
- The D-PND introduced two distinct n-type layers: n^- (low doping, high thickness) and n⁺ (high doping, low thickness).
Material Parameter Calibration:
- Key diamond material parameters (mobility, bandgap, etc.) were set based on established literature.
- The simulation adopted an incomplete ionization model to account for the high activation energy of dopants in diamond, simulating performance at 550 K.
Physical Models Employed:
- Shockley-Read-Hall (SRH) Recombination: Used to model phonon transitions occurring due to traps/defects within the forbidden gap. Electron and hole lifetimes (τ_p and τ_n) were set to 2 x 10^-9 s.
- Auger Recombination: Modeled three-particle transitions involving carrier capture or emission.
- Low-Field Mobility Model: Used to calculate electron (μ_n) and hole (μ_p) mobility based on lattice temperature (T).
- Bandgap Narrowing and Parallel Electric Field Dependence: Included for comprehensive accuracy.
Optimization Variables:
- S-PND: Cathode size (S = 0 to 3 µm), n-type layer depth (D = 100 to 200 nm), and electron concentration (10¹⁷ to 10¹⁸ cm^-3).
- D-PND: Relative distance between n⁺ and n^- layers (S₁), doping concentrations of n⁺ and n^- layers, and relative thicknesses (D₁ and D₂) while maintaining a total JTE depth of 150 nm.

6CCVD Solutions & Capabilities

The successful fabrication of the high-performance D-PND device simulated in this study relies entirely on the ability to produce high-quality, large-area diamond wafers with precise, controlled doping profiles and thin-film epitaxy. 6CCVD (6ccvd.com) is uniquely positioned to supply the necessary materials and engineering services required to transition this TCAD simulation into a functional device.

Applicable Materials

The D-PND structure requires high-quality, low-defect single-crystal diamond (SCD) for vertical device performance, coupled with precise doping control for both p-type and n-type layers.

Component Requirement	6CCVD Material Solution	Key Capability Match
p⁺ Substrate (1 x 10¹⁹ cm^-3)	Heavy Boron-Doped SCD (BDD)	6CCVD provides high-quality SCD substrates with controlled Boron doping for low-resistance Ohmic contacts and base layers.
p^- Drift Layer (1 x 10¹⁶ cm^-3)	Low-Doped SCD Epitaxial Layer	We offer precise control over epitaxial growth to achieve the required 4 µm thickness and low background doping necessary for the high-voltage drift region.
n^-/n⁺ JTE Layers (100 nm / 50 nm)	Phosphorus-Doped SCD Epitaxy	The paper highlights the difficulty of n-type doping (Phosphorus). 6CCVD specializes in MPCVD growth recipes capable of achieving the required thin (50-150 nm) layers with controlled concentrations (10¹⁷ to 10¹⁸ cm^-3).
Device Footprint	Large-Area SCD/PCD Wafers	While the simulation is small-scale, 6CCVD offers SCD and PCD plates/wafers up to 125mm, supporting industrial scaling and high-yield chip cutting.

Customization Potential

The fabrication of the D-PND requires advanced material processing capabilities, all available in-house at 6CCVD:

Precise Thickness Control: The JTE layers require thicknesses as low as 50 nm (0.05 µm). 6CCVD guarantees SCD and PCD epitaxial thickness control from 0.1 µm up to 500 µm, easily accommodating the simulated 50 nm to 4 µm layers.
Surface Quality: The performance of the vertical device and the PN junction interface quality are highly dependent on surface flatness. 6CCVD provides ultra-smooth polishing, achieving surface roughness Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD.
Custom Metalization: The device requires Ohmic contacts (Anode/Cathode). 6CCVD offers internal metalization services, including standard contacts like Ti/Pt/Au, as well as custom layers using W, Cu, or Pd, tailored to specific contact resistance requirements.
Custom Dimensions and Shaping: 6CCVD provides custom laser cutting and shaping services to define the precise electrode geometry (like the S₁ distance optimization) required for optimal JTE performance.

Engineering Support

The successful implementation of this double-layer JTE structure requires deep expertise in diamond epitaxy and device physics, particularly concerning the challenging n-type doping and activation at elevated temperatures (550 K).

Doping Optimization: 6CCVD’s in-house PhD engineering team can assist researchers in optimizing the MPCVD growth parameters (temperature, pressure, gas flow ratios) to achieve the precise 1 x 10¹⁸ cm^-3 (n⁺) and 5 x 10¹⁷ cm^-3 (n^-) phosphorus doping concentrations required for the best BFOM.
Vertical Device Design Consultation: We offer consultation on material selection and stack design for similar high-power vertical diamond PND and Schottky Barrier Diode (SBD) projects, ensuring the supplied material meets the stringent requirements for high V_bd and low R_on.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

This study proposed a novel double-layer junction termination structure for vertical diamond-based PN junction diodes (PND). The effects of the geometry and doping concentration of the junction termination structure on the PNDs’ electrical properties are investigated using Silvaco TCAD software (Version 5.0.10.R). It demonstrates that the electric performances of PND with a single n-type diamond layer are sensitive to the doping concentration and electrode location of the n-type diamond. To further suppress the electric field crowding and obtain a better balance between breakdown voltage and on-resistance, a double-layer junction termination structure is introduced and evaluated, yielding significantly improved electronic performances. Those results provide some useful thoughts for the design of vertical diamond PND devices.

Tech Support

Original Source

DOI: https://doi.org/10.3390/electronics13091703

References

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