Diamond p-Type Lateral Schottky Barrier Diodes With High Breakdown Voltage (4612 V at 0.01 mA/Mm)

At a Glance

Metadata	Details
Publication Date	2023-08-31
Journal	IEEE Electron Device Letters
Authors	Zhuoran Han, C. Bayram
Institutions	University of Illinois Urbana-Champaign
Citations	26
Analysis	Full AI Review Included

Technical Analysis and Documentation: High Breakdown Voltage Diamond Lateral SBDs

Executive Summary

This documentation analyzes the fabrication and performance of p-type lateral diamond Schottky Barrier Diodes (SBDs) achieving a record high breakdown voltage (V_br) of 4612 V, enabled by advanced MPCVD growth and edge termination techniques.

Record V_br Achievement: A breakdown voltage of 4612 V was demonstrated in a lateral p-type diamond SBD, significantly exceeding previously reported diamond SBD performance.
Field Plate Effectiveness: The incorporation of a 300 nm Al₂O₃ field plate was critical, increasing V_br by over 300% (from 1159 V to 4612 V) by reducing peak electric field crowding by a simulated 56%.
Material Requirements: Devices rely on highly controlled, low-doped (p^-) SCD drift layers (2 µm thick) and heavily doped (p⁺) SCD contact layers grown via MPCVD.
Contact Performance: Excellent ohmic contact performance was achieved using a Ti/Pt/Au stack, yielding a specific contact resistance of 1.25 x 10^-4 Ω-cm².
High Rectification: The fabricated SBDs exhibit robust room temperature performance with a rectifying ratio greater than 10⁷ and stable reverse leakage current density below 0.01 mA/mm.
Application Focus: This research validates diamond’s potential for next-generation high-power, high-voltage electronic devices, particularly in lateral configurations where V_br is scaled by contact separation.

Technical Specifications

Parameter	Value	Unit	Context
Peak Breakdown Voltage (V_br)	4612	V	With Al₂O₃ Field Plate
V_br (Baseline)	1159	V	Without Field Plate
Specific On-Resistance (R_ON)	527	Ω-cm²	With Field Plate (Room Temp)
Specific Ohmic Contact Resistance	1.25 ± 0.98 x 10^-4	Ω-cm²	Ti/Pt/Au Stack
Rectifying Ratio	> 10⁷	Dimensionless	At Room Temperature (± 5 V)
Leakage Current Density (V_br limit)	< 0.01	mA/mm	Prior to Breakdown
Peak Forward Current Density	5.39	mA/mm	At 40 V Forward Bias (200 °C)
Schottky Barrier Height (SBH)	1.02 ± 0.01	eV	Mo/Pt/Au Contact
p^- Drift Layer Thickness	2	µm	[B] < 8 x 10¹⁵ cm^-3
p⁺ Contact Layer Thickness	200	nm	[B] ~ 3 x 10²⁰ cm^-3
RMS Surface Roughness	7.5	nm	Epitaxial Layer
Field Plate Thickness	300	nm	Al₂O₃
Ohmic-Schottky Separation (d)	80	µm	Drift Region Length

Key Methodologies

The high-performance lateral SBDs were fabricated using a multi-step MPCVD growth and advanced cleanroom microfabrication process:

Substrate Preparation: Use of 3 x 3 mm² Type Ib (100) High Pressure High Temperature (HPHT) diamond substrates.
Drift Layer Epitaxy (MPCVD): Growth of a 2 µm p^- drift layer via Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD).
Contact Layer Selective Growth: Selective MPCVD growth of a 200 nm heavily Boron-Doped (p⁺) diamond layer to define the ohmic contact regions.
Ohmic Metalization: E-beam evaporation of a Ti (30 nm) / Pt (30 nm) / Au (100 nm) stack.
Contact Annealing: Thermal annealing of ohmic contacts at 450 °C in an Argon (Ar) ambient for 50 minutes.
Field Plate Formation: E-beam evaporation and lift-off of a 300 nm Al₂O₃ dielectric layer for edge termination.
Surface Treatment: Ozone treatment of the exposed diamond surface at room temperature for 1.5 hours to ensure stable oxygen termination prior to Schottky deposition.
Schottky Metalization: E-beam evaporation of the Schottky metal stack: Mo (50 nm) / Pt (50 nm) / Au (100 nm).

6CCVD Solutions & Capabilities

This research demonstrates the critical role of high-quality, precisely doped SCD layers and advanced metalization techniques in achieving extreme breakdown voltages. 6CCVD is uniquely positioned to supply the necessary materials and processing services to replicate and scale this high-power diamond technology.

Applicable Materials

To replicate or extend this high-voltage lateral SBD architecture, 6CCVD recommends the following materials, all grown via high-purity MPCVD:

Device Layer Requirement	6CCVD Material Solution	Key Specification Match
Drift Layer (p^-)	Electronic Grade Single Crystal Diamond (SCD)	Ultra-low nitrogen concentration; precise Boron doping control ([B] < 8 x 10¹⁵ cm^-3).
Contact Layer (p⁺)	Heavy Boron-Doped Diamond (BDD)	High doping concentration ([B] ~ 3 x 10²⁰ cm^-3) for low specific ohmic contact resistance.
Substrate	SCD or HPHT Substrates	High-quality, low-defect (100) orientation substrates for homoepitaxial growth.

Customization Potential

The success of this device hinges on precise layer thickness, doping control, and complex metal stacks. 6CCVD’s in-house capabilities directly address these requirements:

Thickness Control: The paper utilized a 2 µm drift layer and a 200 nm contact layer. 6CCVD offers SCD and PCD thickness control ranging from 0.1 µm up to 500 µm, ensuring precise epitaxial layer design for optimal R_ON and V_br trade-offs.
Advanced Metalization: The device requires two distinct metal stacks (Ohmic: Ti/Pt/Au; Schottky: Mo/Pt/Au). 6CCVD provides custom, multi-layer metalization services, including Au, Pt, Pd, Ti, W, and Cu, tailored to specific contact requirements (e.g., Schottky barrier height or ohmic performance).
Scaling and Dimensions: While the research used small 3 x 3 mm² substrates, 6CCVD can supply inch-size SCD and PCD plates up to 125mm in diameter, enabling commercial scaling of lateral power devices.
Surface Quality: The paper noted that RMS roughness (7.5 nm) may limit stable leakage current. 6CCVD offers ultra-smooth polishing services, achieving Ra < 1 nm for SCD, crucial for minimizing surface leakage paths and improving reliability in high-field applications.

Engineering Support

The achievement of 4612 V breakdown voltage in this p-type lateral SBD is a major step for diamond power electronics. 6CCVD’s in-house PhD team specializes in material science and device physics, offering expert consultation for projects targeting:

High-Voltage Edge Termination: Assistance in selecting optimal dielectric materials (beyond Al₂O₃) and designing field plate geometries for maximum electric field reduction.
Drift Region Optimization: Modeling and material selection support to optimize drift layer thickness and doping concentration to simultaneously reduce R_ON and maintain high V_br, moving closer to the theoretical diamond limit.
Custom Doping Profiles: Development of complex, tailored Boron-Doped Diamond (BDD) profiles necessary for advanced power device structures (e.g., JFETs, MOSFETs, and pseudo-vertical SBDs).

Call to Action: For custom specifications or material consultation regarding high-power diamond Schottky Barrier Diodes or similar high-voltage projects, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Diamond p-type lateral Schottky barrier diodes (SBDs) with a 2-μm-thick drift layer are fabricated with and without Al2O3 field plates. Schottky contacts composed of Mo (50 nm) / Pt (50 nm) / Au (100 nm) showed a barrier height of 1.02 ± 0.01 eV and ohmic contacts of Ti (30 nm) / Pt (30 nm) / Au (100 nm) achieved a specific ohmic contact resistance of 1.25 ± 0.98 × 10-4 Ω-cm2. Their forward and reverse bias characteristics are studied in detail. Both SBDs, with and without Al2O3 field plates, exhibit rectifying ratios larger than 107 at room temperature, and a peak current density of 5.39 mA/mm under 40 V forward bias at 200 °C. The leakage current density at room temperature is stable at approximately 0.01 mA/mm for both diodes. The SBD without the Al2O3 field plate exhibited a breakdown voltage of 1159 V, while the SBD with the Al2O3 field plate is stable under a reverse voltage of 4612 V, which is higher than many diamond SBDs previously reported.

Tech Support

Original Source

DOI: https://doi.org/10.1109/led.2023.3310910