RECENT PROGRESS OF DIAMOND DEVICE TOWARD POWER APPLICATION

At a Glance

Metadata	Details
Publication Date	2015-08-26
Authors	Julien Pernot, Kazuhiro Ikeda, Alexandre Fiori, Aboulaye Traoré, N Tatsumi
Institutions	Conductive Composites (United States)
Citations	2
Analysis	Full AI Review Included

Technical Documentation: Diamond Devices for Power Applications

Based on: HAL Id: hal-00994084v1, “Recent progress of diamond device toward power application”

6CCVD analyzes the structural and electrical breakthroughs achieved in diamond-based power devices, including Schottky diodes, Boron $\delta$-FETs, and the critical demonstration of an electron inversion layer in diamond MOS structures. This research confirms diamond’s definitive position as the ultimate wide band gap semiconductor for high-power, high-frequency systems.

Executive Summary

Ultimate Semiconductor Validation: Diamond is validated as the superior wide band gap material, exhibiting a breakdown field (E_B) of 10 MV/cm and exceptional thermal conductivity ($\lambda$ = 22 W/cm·K), leading to a Baliga’s Figure of Merit (BFM) 23,000 times higher than silicon.
High-Voltage Performance: Pseudo-vertical Schottky diodes were successfully fabricated on homoepitaxial SCD, demonstrating record-breaking reverse blocking voltages up to 10 kV before avalanche breakdown.
Fundamental Breakthrough (MOSFET): For the first time, researchers successfully achieved an electron inversion layer in a p-type diamond MOS structure (Al/Al₂O₃/p-type D), opening the path to viable diamond MOSFET fabrication.
Advanced Doping Architectures: The devices utilize complex layered structures, including low boron-doped (10¹⁴-10¹⁶ cm^-3) epilayers and highly degenerate Boron $\delta$-doping layers (>5 x 10²⁰ cm^-3) for enhanced conductivity and quantum confinement.
MPCVD and Interface Control: Success relied critically on precise MPCVD growth of homoepitaxial (100) SCD, coupled with advanced surface passivation techniques (VUV ozone treatment) to minimize interface trap states.
Field Effect Transistor Progress: Investigation into Boron $\delta$-doped FETs (metallic channel) confirmed the potential for combining high carrier mobility with large carrier concentration for high-frequency switch applications.

Technical Specifications

Parameter	Value	Unit	Context
Bandgap (E_G)	5.45	eV	Intrinsic Diamond Property
Theoretical Breakdown Field (E_B)	10	MV/cm	Ultimate Material Limit (vs. SiC: 3, GaN: 2)
Thermal Conductivity ($\lambda$)	22	W/cm·K	Highest known semiconductor thermal dissipation
Hole Mobility ($\mu_{p}$)	2000	cm²/V·s	Room Temperature
Baliga’s Figure of Merit (BFM)	23068	Si=1	Metric for loss in high power operation
Maximum Blocking Voltage	10	kV	Achieved by Schottky Diode (Reverse Regime)
Peak Calculated Electric Field	7.5	MV/cm	At the center of the diode during 10 kV test
Schottky Contact Diameter	150	µm	For I-V measurements
MPCVD Growth Temperature	830	°C	Homoepitaxial Layer on HPHT substrate
MPCVD Gas Mixture	4% CH₄ in H₂	N/A	Reactor Feed Gas Ratio
MPCVD Pressure	30	torr	Growth environment pressure
Highly Boron Doped Layer (Metallic)	>5 x 10²⁰	cm^-3	Used for $\delta$-layers and enhanced contacts
Low Doped Epilayer Thickness (p’)	13.6	µm	Critical thickness for high voltage blocking layer
Net Acceptor Concentration (N_A-N_D)	2.5 x 10¹⁴ to 4 x 10¹⁵	cm^-3	Fluctuating level in the first 6 µm of epilayer

Key Methodologies

The research relied on highly controlled MPCVD growth and specific post-processing techniques to create advanced device architectures:

Substrate Preparation: Use of 3x3 mm² (100) oriented Ib High-Pressure High-Temperature (HPHT) diamond substrates as the base material.
Homoepitaxial Growth: Active layers were deposited using Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD) at 830 °C and 30 torr, utilizing a 4% CH₄ in H₂ gas mixture.
Doping Control: Boron concentration was precisely modulated from low p-type (10¹⁴ cm^-3) up to metallic levels (>5 x 10²⁰ cm^-3) to form intrinsic (i), p-type blocking layers, and highly conductive $\delta$-channels.
Surface Passivation: Superior electrical performance in the Schottky diodes was achieved by oxidizing the surface using ozone produced by VUV light treatment prior to metal deposition.
Ohmic Contact Formation: Ti/Au Ohmic contacts were deposited and subjected to a post-deposition annealing process (1 hour at 750 °C under vacuum) after acid cleaning.
Schottky Metalization: Gold (Au) was deposited as the Schottky contact metal through a metallic mask (150 µm diameter) onto the VUV-treated epilayer.
Dielectric/Gate Stack (MOSFET): The MOSFET structure required the deposition of an Al₂O₃ dielectric layer followed by an Aluminum (Al) gate electrode on the p-type SCD layer, referenced against a Ti/Pt/Au contact.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials necessary to replicate, optimize, and commercialize the high-power devices described in this research. Our capabilities directly address the material and processing requirements for high-voltage diodes and next-generation diamond FETs.

Applicable Materials & Doping Profiles

To replicate or advance the devices detailed in this study (Schottky diodes, $\delta$-FETs, and MOS structures), 6CCVD recommends the following high-precision materials, all grown via MPCVD:

Optical Grade Single Crystal Diamond (SCD): Required for the intrinsic (i) and low-doped (p’) layers, ensuring the low defect density and high crystal quality necessary for achieving E_B = 10 MV/cm.
Heavy Boron Doped SCD (BDD): Essential for forming the metallic $\delta$-layers (doping >5 x 10²⁰ cm^-3) used in the $\delta$-FET channel, providing the high conductivity and confinement required for low R_on.
Custom Substrate Engineering: Supply of precisely oriented (100) SCD or PCD substrates up to 125 mm, mirroring the structural requirements of the Ib HPHT substrates used in the study.

Customization Potential for Power Device Fabrication

The research demonstrates that device success hinges on precise dimensioning and complex metal/dielectric integration. 6CCVD provides the following engineering support:

Research Requirement	6CCVD Capability	Engineering Advantage
Precise Layer Thickness	Custom Thickness SCD/PCD: Thickness control from 0.1 µm up to 500 µm (SCD) or up to 10 mm (Substrates).	Enables accurate replication of the 13.6 µm blocking layers and thin $\delta$-channels required for high-voltage performance.
Sharp Doping Gradient	Advanced MPCVD Doping: Ability to produce abrupt interface transitions between highly doped and intrinsic layers necessary for optimized space charge regions and $\delta$-FET confinement.	Supports optimization of the forward/reverse bias characteristics of stacked diodes for maximum current density and blocking voltage.
Multi-layer Metalization	Integrated Metalization Services: Internal deposition of required metal stacks (Ti/Au Ohmic, Au Schottky) and the precursor layers for specialized gate stacks (Al/Al₂O₃).	Delivers research-ready wafers with custom Au, Pt, Pd, Ti, or Cu contacts, accelerating device prototyping and testing cycles.
Scaling Up	Large Format Processing: Wafers and plates available up to 125 mm (PCD), enabling the scale-up of successful 3x3 mm² lab prototypes to production volumes for commercial power modules.	Facilitates the industrial transition of high-power diamond rectifiers and switches.

Engineering Support & Call to Action

6CCVD’s in-house PhD engineering team possesses deep expertise in MPCVD growth parameters, doping profiles, and surface treatments critical for high-voltage devices. We can assist researchers and manufacturers in selecting the optimal SCD material grade and processing parameters necessary for high-power Schottky diodes, $\delta$-FETs, and the promising new diamond MOSFET technology.

We offer global shipping (DDU default, DDP available) to ensure timely delivery of custom materials worldwide.

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

View Original Abstract

The state of the art of the Institut Néel research activity in the field of diamond power devices will be described and discussed. The active layers of the device are based on boron-doped monocristalline (100) diamond (with doping level varying between 1014 to 1021 cm-3) grown on Ib high temperature high pressure (HPHT) diamond substrate. The progresses done on diamond/metal interface, diamond/dielectric interface, or sharp gradient doping, permit recently the fabrication of original structures and devices, which will be detailed here (Schottky diode, boron doped δ-FET and MOS capacitance).

Tech Support

Original Source

DOI: None