Impedance Response and Phase Angle Determination of Metal-Semiconductor Structure with N-Doped Diamond Like Carbon Interlayer

At a Glance

Metadata	Details
Publication Date	2024-01-30
Journal	Gazi University Journal of Science Part A Engineering and Innovation
Authors	Nuray Urgun, A. Feizollahi Vahid, Jaafar Alsmael, Barış Avar, Serhat Orkun Tan
Institutions	Bülent Ecevit University, Karabük University
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Performance Diamond-Based MIS Structures

This document analyzes the research on Metal-Semiconductor Structures utilizing N-Doped Diamond-Like Carbon (N:DLC) interlayers for tunable impedance response, connecting the findings directly to 6CCVD’s advanced MPCVD diamond material solutions.

Executive Summary

Core Achievement: Successful fabrication and characterization of an Al/N:DLC/p-Si/Au Metal-Insulator-Semiconductor (MIS) structure, demonstrating tunable electrical conduction and selective frequency response.
Material Focus: N-doped Diamond-Like Carbon (N:DLC) was employed as a high-quality dielectric interlayer to enhance Schottky Barrier Diode (SBD) performance, proving the efficacy of diamond-based materials in regulating charge transitions.
Electrical Performance: The device exhibited highly capacitive behavior in the inversion stage (Phase Angle up to 89.89°) and tunable conductivity in the accumulation stage, allowing for frequency-adjustable working conditions.
Wide Operating Range: Measurements were conducted across a broad spectrum of voltage (-3V to +4V) and frequency (1 kHz to 1 MHz), confirming stability and performance across different conduction regimes.
Impedance Control: Complex impedance was shown to decrease significantly with rising bias and frequency, ranging from 1.8 MΩ down to 2 kΩ at 1 MHz, indicating rising conduction performance.
Fabrication Method: The structure was fabricated using a combination of electrochemical deposition (for N:DLC), RF magnetron sputtering (Au back contact), and thermal evaporation (Al rectifier contact).

Technical Specifications

The following hard data points were extracted from the impedance spectroscopy analysis of the Al/N:DLC/p-Si/Au MIS structure:

Parameter	Value	Unit	Context
Operating Voltage Range	-3 to +4	V	DC Bias Sweep
Operating Frequency Range	1 kHz to 1	MHz	AC Signal Range
Maximum Complex Impedance	1.8	MΩ	Observed at low frequency/reverse bias
Minimum Complex Impedance	2	kΩ	Observed at 1 MHz
Maximum Phase Angle ($\theta$)	89.89	°	At -3V, 10 kHz (Highly Capacitive Inversion)
Minimum Phase Angle ($\theta$)	0.65	°	At 3.95V, 1 kHz (Highly Conductive Accumulation)
Interfacial Layer Width ($d_i$)	1.0	µm	N:DLC thickness (Constant, $10^{-6}$ m)
Schottky Contact Area (A)	0.00785	cm²	Calculated ($\pi r^2$)
Vacuum Capacitance ($C_0$)	6.95	pF	Calculated
Substrate Material	Boron-doped p-type Si	N/A	<100> alignment, ≈300 µm thickness

Key Methodologies

The Al/N:DLC/p-Si/Au MIS structure was fabricated and characterized using the following sequence of steps:

Substrate Preparation: A boron-doped p-type Si substrate (<100> surface alignment, ≈300 µm thickness) was used as the negative electrode.
N:DLC Interlayer Deposition: The N:DLC thin film was deposited on the p-Si substrate via electrolysis (electrochemical deposition).
- Precursor: 100 mL methanol (CH₃OH, 99.5% N) and 200 mg urea.
- Process: Stirred for 15 minutes.
Back Contact Formation (Au): Au was deposited via RF magnetron sputtering at 550 V.
- Post-Processing: Annealing at 550 °C was performed to achieve better ohmic connection.
Rectifier Contact Formation (Al): High purity Al contacts were formed via thermal evaporation to complete the MIS structure.
Electrical Characterization: Measurements were conducted using an HP 4192A LF impedance analyzer.
- Data Collection: C($\omega$)-V, G($\omega$)-V, C($\omega$)-f(Hz), and G($\omega$)-f(Hz) measurements were used to calculate impedance and phase angle.

6CCVD Solutions & Capabilities

The successful integration of N:DLC as a functional interlayer highlights the critical role of diamond-based materials in next-generation high-frequency, high-power electronics, particularly for tunable SBDs and filter components. 6CCVD offers MPCVD diamond materials that provide superior crystallinity, purity, and thermal stability compared to the amorphous DLC used in this study, enabling researchers to push performance boundaries further.

Applicable Materials for Replication and Extension

To replicate or significantly extend this research, 6CCVD recommends utilizing our high-quality MPCVD materials, which offer precise control over doping and thickness, crucial for optimizing the dielectric and conductive properties of the interlayer and substrate.

Application Requirement	6CCVD Material Solution	Key Benefit
High-Performance Substrate/Semiconductor	Boron-Doped Diamond (BDD)	Replaces p-Si. Offers extreme thermal stability, high carrier mobility, and tunable conductivity (heavy doping for ohmic contacts, light doping for active regions). Available up to 500 µm thickness.
High-Quality Dielectric Interlayer	Optical Grade Single Crystal Diamond (SCD)	Provides ultra-low loss, high dielectric strength, and superior purity (Ra < 1 nm polishing available) compared to N:DLC, minimizing surface states and improving barrier height uniformity.
Large-Area MIS/SBD Arrays	Polycrystalline Diamond (PCD)	Cost-effective solution for large-scale device fabrication. 6CCVD offers PCD wafers up to 125mm diameter with polishing down to Ra < 5 nm.

Customization Potential for Device Optimization

The research requires precise control over contact geometry and material interfaces. 6CCVD’s in-house capabilities directly address these needs:

Custom Metalization Services: The device utilized Au and Al contacts. 6CCVD offers internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu. This allows researchers to optimize the Schottky barrier height and ohmic contact resistance, critical for tuning the device’s frequency response and conduction regimes (Inversion, Depletion, Accumulation).
Precise Dimensional Control: The Schottky contact area was $0.00785$ cm². 6CCVD provides custom laser cutting and patterning services to achieve highly precise device geometries and ensure uniformity across wafers up to 125mm.
Thickness Control: The N:DLC layer was 1 µm thick. 6CCVD offers SCD and PCD films with precise thickness control from 0.1 µm up to 500 µm, allowing for fine-tuning of the dielectric capacitance ($C_0$) and depletion region effects.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in the physics of diamond interfaces and wide-bandgap semiconductor devices. We offer consultation services to assist researchers in:

Equivalent Circuit Modeling: Assisting with material selection and design parameters to achieve specific capacitive, resistive, or inductive responses required for band-enhancing filter component designs, as suggested by the paper’s conclusion.
Interface State Management: Optimizing diamond surface termination and doping profiles to minimize interface states ($N_{ss}$) and relaxation behavior, which were identified as key factors causing deviations in the impedance plots.
High-Frequency Device Design: Providing material specifications necessary to extend the operating frequency range beyond the 1 MHz limit tested in this study, leveraging the intrinsic high-frequency capabilities of MPCVD diamond.

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

View Original Abstract

With their superior properties over p-n barriers, Schottky Barrier Diodes have a wide usage area, especially as a test tool to produce better-performance devices. The main performance parameter of these devices is measured by their conduction, which can develop with an interlayer addition through the sandwich design. Regarding the DLC, which also has outstanding specifications under thermal, chemical, and physical conditions, is a good candidate for interlayer tailoring, specifically when used with doping atoms. Thus, this study investigates the impedance response of the fabricated device with an N-doped DLC interlayer by employing the electrochemical technique as a combination of electrolysis, RF magnetron sputtering, and thermal evaporation. The measurements were conducted for broad scales of voltage and frequency corresponding between (-3V) and (+4V) and 1kHz and 1MHz, respectively. According to the impedance analysis, complex impedance decreases by rising bias and frequency, from 1.8 MΩ to 2 k Ω at 1MHZ due to the additional insulating layer. At the same time, the phase angle indicates the quality of the dielectric layer with an average of 81.36  for the sample logarithmic frequency values with an almost constant-like trend in the inversion stage. In comparison, it reduces to an average of 30.25  after the depletion stage by showing the rising conductivity. Moreover, it has some unexpected rising values at the strong accumulation stage, possibly due to the deposited thin film’s unique structure. The supported results by phase angle changes, showing frequency-adjustable working conditions, may offer that selective electrical conduction can be tuned.

Tech Support

Original Source

DOI: https://doi.org/10.54287/gujsa.1393292