Schottky Barrier Height Analysis of Diamond SPIND Using High Temperature Operation up to 873 K

At a Glance

Metadata	Details
Publication Date	2020-01-01
Journal	IEEE Journal of the Electron Devices Society
Authors	Mohamadali Malakoutian, Manpuneet Benipal, Franz A. Koeck, R. J. Nemanich, Srabanti Chowdhury
Institutions	Stanford University, Arizona State University
Citations	25
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Temperature Diamond SPIND

Executive Summary

This research successfully demonstrates the exceptional thermal stability and high-power performance of a diamond Schottky PIN Diode (SPIND), validating diamond’s role in extreme environment power electronics.

Extreme Temperature Operation: Stable, explicit diode rectification was demonstrated up to 723 K, with functional operation and stability confirmed up to 873 K (600 °C).
High Current Density: The SPIND achieved an excellent forward current density exceeding 3000 A/cm² at 8 V, confirming high-power capability.
Exceptional Stability: The device exhibited no degradation in I-V characteristics after 10 high-temperature cycles, totaling 120 hours of exposure up to 873 K.
High Rectification: Rectification factors were measured at >10⁹ at 298 K and 1100 at 673 K, indicating excellent diode quality.
Barrier Inhomogeneity Confirmed: The study utilized Tung’s modified thermionic emission model and Conductive Atomic Force Microscopy (C-AFM) to confirm and analyze inhomogeneous Schottky barrier heights (SBHs).
Model Validation: The modified model successfully resolved the discrepancy in the Richardson’s constant, yielding an extracted value (A** = 81.16 ± 8.9 A/cm²·K²) that closely matches the theoretical value (90 A/cm²·K²).

Technical Specifications

The following hard data points were extracted from the analysis of the diamond Schottky PIN Diode (SPIND) performance and fabrication.

Parameter	Value	Unit	Context
Maximum Operating Temperature	873	K	Stable operation demonstrated
Forward Current Density (J_F)	>3000	A/cm²	Measured at 8 V (Device #1)
Rectification Factor (R)	>10⁹	N/A	Measured at 298 K (Room Temperature)
Rectification Factor (R)	1100	N/A	Measured at 673 K
Minimum Specific On-Resistance (R_on.sp)	5.7	mΩ·cm²	Achieved at 873 K (1.5 V bias)
Substrate Doping (p-type)	~1 x 10²⁰	cm⁻³	Highly Boron-Doped (Type IIb)
N-Layer Doping (n-type)	<10¹⁹	cm⁻³	Phosphorus-Doped
Intrinsic (i) Layer Thickness	500	nm	CVD Grown
N-Layer Thickness	100	nm	CVD Grown
Extracted Richardson’s Constant (A**)	81.16 ± 8.9	A/cm²·K²	Using Tung’s Inhomogeneity Model
Metal Stack Composition	Ti/Pt/Au	N/A	50nm/50nm/150nm

Key Methodologies

The diamond SPIND structure was fabricated using high-quality CVD growth on HPHT substrates, followed by standard semiconductor processing techniques.

Substrate Selection: Used (100)-oriented Type IIb Boron-Doped diamond substrate (p-type, ~1 x 10²⁰ cm⁻³).
CVD Growth of I-Layer: Intrinsic diamond layer (500 nm) grown in three stages using H₂ (392-400 sccm), CH₄ (0.75 sccm), and O₂ (0.75 sccm) at 60 Torr pressure and temperatures ranging from 704 °C to 807 °C.
CVD Growth of N-Layer: N-type phosphorus-doped layer (100 nm, <10¹⁹ cm⁻³) grown in two stages using H₂ (357-400 sccm), CH₄ (7.0 sccm), and TMP/H₂ (40 sccm) at 65-75 Torr pressure and temperatures up to 1025 °C.
Mesa Isolation: Al hard mask patterning followed by Inductively Coupled Plasma / Reactive Ion Etching (ICP/RIE) using O₂/SF₆ plasma, etching down to the middle of the i-layer.
Surface Treatment: Samples were immersed in a H₂SO₄:HNO₃ (3:1) acid mixture at 220 °C to achieve oxygen termination and remove surface conduction.
Metal Contact Deposition: Ti/Pt/Au (50nm/50nm/150nm) metal contacts were deposited via e-beam evaporation and patterned using a lift-off process.
Contact Annealing: Metal contacts were annealed at 850 °C to ensure stability and adhesion.
Characterization: I-V measurements were conducted from 298 K to 873 K using a high-temperature stage. Conductive AFM (C-AFM) was used to map local current flow and confirm barrier inhomogeneity.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and fabrication services required to replicate, optimize, and scale this high-temperature SPIND technology. Our capabilities directly address the material and processing needs highlighted in this research.

Requirement from Paper	6CCVD Solution & Capability	Technical Advantage for Replication/Scaling
Heavily Doped Substrate (p-type, ~10²⁰ cm⁻³)	Heavy Boron-Doped Diamond (BDD) Substrates. We offer BDD layers and substrates up to 10mm thick, ensuring high conductivity for the p+ layer.	Guarantees low series resistance and efficient backside ohmic contact, critical for achieving high forward current density (>3000 A/cm²).
High-Quality Intrinsic (i) Layer (500 nm)	High Purity Single Crystal Diamond (SCD). We supply SCD layers with thicknesses from 0.1 µm up to 500 µm, polished to Ra < 1 nm.	Provides the necessary wide bandgap material quality to minimize defects, ensuring high rectification factors (>10⁹) and high breakdown voltage stability at extreme temperatures.
Custom N-Type Doping (Phosphorus)	Custom MPCVD Doping Services. 6CCVD can precisely control the incorporation of dopants (e.g., Phosphorus) to achieve the required N-type concentration (<10¹⁹ cm⁻³).	Allows researchers to fine-tune the doping profile and layer thickness (100 nm) necessary for optimizing the Schottky barrier height (SBH) and ideality factor (n).
Custom Metalization Stack (Ti/Pt/Au)	In-House Metalization Capability. We routinely deposit complex metal stacks including Ti, Pt, and Au, as well as Pd, W, and Cu.	We can replicate the exact Ti/Pt/Au stack (50nm/50nm/150nm) used for the stable high-temperature Schottky contact, ensuring thermal reliability up to 873 K.
Large Area Device Scaling	Large Format PCD/SCD Wafers. We offer plates and wafers up to 125mm (PCD) and large-area SCD, polished to Ra < 5 nm (PCD).	Enables the transition from research-scale devices to commercial-scale power modules, maintaining uniformity and quality across large areas.
Engineering Support for SBH Control	In-House PhD Engineering Team. Our experts specialize in diamond surface termination and interface engineering, crucial for controlling SBH inhomogeneity.	Provides direct consultation to assist engineers in material selection and surface preparation protocols to achieve desired device characteristics and thermal stability for high-temperature applications (e.g., Venus environment).

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

View Original Abstract

In this work, the high temperature performance of a diamond Schottky PIN diode is reported in the range of 298-873 K. The diamond diode exhibited an explicit rectification up to 723 K with an excellent forward current density of >3000 A/cm2. The stability of the diode was investigated by exposing the sample to high temperature cycles (up to 873 K) for more than 10 times (totaling up to 120 hours), which exhibited no change between the I-V characteristics measured in each cycle. The dependence of ideality factor and Schottky barrier height on temperature along with an extracted Richardson’s constant much smaller than the theoretical value (0.0461 A/cm2.K2), motivated us to study the possible reason for this anomaly. A modified thermionic emission model following Tung’s analysis was used to explain the experimental observations. The model assumed the presence of inhomogeneous Schottky barrier heights leading to a reduced effective area and yielded a Richardson’s constant closer to the theoretical value. Conductive atomic force microscopy studies were conducted, which concurred with the electrical data and confirmed the presence of inhomogeneous Schottky barrier heights.

Tech Support

Original Source

DOI: https://doi.org/10.1109/jeds.2020.2999269

References

2017 - Schottky-barrier inhomogeneities in WC/p-diamond at high temperature