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6CCVD Research

Impact of the Deposition Temperature on the Structural and Electrical Properties of InN Films Grown on Self-Standing Diamond Substrates by Low-Temperature ECR-MOCVD

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2020-12-04
JournalCoatings
AuthorsShuaijie Wang, Fuwen Qin, Yizhen Bai, Dong Zhang, Jingdan Zhang
InstitutionsDalian University of Technology, Shenyang Institute of Engineering
Citations6
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study investigates the critical role of deposition temperature in optimizing Indium Nitride (InN) thin films grown on self-standing diamond substrates using Electron Cyclotron Resonance Plasma-Enhanced Metal Organic Chemical Vapor Deposition (ECR-PEMOCVD).

  • Core Value Proposition: The use of self-standing diamond substrates provides superior thermal conductivity, making the resulting InN films highly attractive for high-power, high-frequency electronic and optoelectronic devices.
  • Methodology: InN films were grown using ECR-PEMOCVD, which allows for low-temperature deposition (200 °C to 600 °C) necessary to inhibit InN decomposition and nitrogen volatilization. Inert N2 was used as the nitrogen source.
  • Optimal Temperature: The optimal deposition temperature was identified as 400 °C, yielding the best combination of structural, morphological, and electrical properties.
  • Structural Achievement: Films grown at 400 °C exhibited the highest crystallinity, characterized by strong c-axis preferential orientation (InN (0002) peak) and the lowest Full Width at Half Maximum (FWHM) of 0.17°.
  • Morphological Achievement: The optimal films showed a smooth surface morphology with uniformly dense grains, achieving a minimum Root Mean Square (RMS) roughness of 3.7 nm.
  • Electrical Performance: The best electrical properties were recorded at 400 °C, including a maximum electron mobility of 48.5 cm2/(V·s) and the lowest carrier concentration (0.92 x 1020 cm-3).
  • Bonding Confirmation: XPS analysis confirmed the good crystalline quality of the 400 °C film, showing a significantly higher intensity for the In-N bond (444.5 eV) compared to the In-In bond (443.3 eV).

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Growth MethodECR-PEMOCVDN/ALow-temperature plasma-enhanced growth.
Substrate MaterialPolycrystalline DiamondN/ASelf-standing, high thermal conductivity.
Optimal Deposition Temperature400°CYields highest crystallinity and mobility.
Film Thickness (Maximum)~350nmFinal thickness of the InN layer.
InN Film Orientationc-axis (0002)N/AHighly preferential orientation at 400 °C.
Optimal FWHM (InN (0002))0.17°Indicator of highest crystallinity (at 400 °C).
Optimal Grain Size (d)47nmCalculated via Scherrer’s formula (at 400 °C).
Optimal RMS Roughness3.7nmMinimum surface roughness (at 400 °C, AFM).
Optimal Electron Mobility48.5cm2/(V·s)Maximum mobility achieved (at 400 °C).
Optimal Carrier Concentration0.92 x 1020cm-3Minimum concentration achieved (at 400 °C).
Film Stress (Optimal)-1.96GPaCompressive stress (at 400 °C).
InN Band Gap (Reported)~0.7eVNarrow band gap, enabling near-infrared applications.
Lattice Mismatch (Diamond (111) vs InN (0002))19.2%High mismatch requiring buffer layer growth.
Magnetic Field Intensity (Hall Test)0.338TUsed for Van der Pauw Hall effect measurement.

Key Methodologies

Section titled “Key Methodologies”

The InN thin films were prepared on self-standing polycrystalline diamond substrates using a multi-step ECR-PEMOCVD process:

  1. Substrate Preparation:

    • Diamond Source: Thick diamond films (0.5-0.8 mm) prepared by DC glow discharge PCVD on Mo substrates, followed by laser stripping to achieve self-standing status.
    • Polishing/Cleaning: Mechanical polishing of the nucleation surface, followed by chemical immersion (3:1 sulfuric acid/phosphoric acid mixture for 24 h) and sequential ultrasonic cleaning (toluene, acetone, ethanol, deionized water).
    • In-situ Plasma Rinse: Substrates were rinsed using H2 plasma (60 sccm H2 flow, 650 W microwave power) for 0.5 h at room temperature.

  2. Precursor Management:

    • Indium Source: Trimethyl Indium (TMIn). Temperature was precisely maintained at 20 ± 1 °C using a semiconductor cold trap.
    • Nitrogen Source: High-purity inert N2 gas.
    • Plasma Generation: ECR discharge was used to generate high-density, activated nitrogen ions, crucial for low-temperature InN formation.

  3. Buffer Layer Growth:

    • Purpose: To mitigate the 19.2% lattice mismatch between InN and diamond.
    • Conditions: Room temperature, 30 min duration, 60 sccm N2 flow, 0.3 sccm TMIn flow.

  4. InN Film Growth:

    • Duration: 180 minutes.
    • Variable Parameter: Deposition temperature varied from 200 °C to 600 °C.
    • Fixed Parameters: 650 W microwave power, 0.6 sccm TMIn flow, 100 sccm N2 flow.

  5. Characterization:

    • Structural: Reflection High-Energy Electron Diffraction (RHEED) and X-ray Diffraction (XRD) were used to assess preferential orientation, FWHM, and internal stress.
    • Morphological: Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) determined surface island density, grain structure, and RMS roughness.
    • Electrical: Hall effect measurement (Van der Pauw method) was used to determine n-type conductivity, carrier concentration, and electron mobility.
    • Chemical Bonding: X-ray Photoelectron Spectroscopy (XPS) confirmed In-N and In-In bonding characteristics.

Commercial Applications

Section titled “Commercial Applications”

This research focuses on developing high-performance Group III nitride materials (InN) integrated with diamond, targeting applications where thermal management is critical for device longevity and power handling.

  • High-Power/High-Frequency Electronics:
    • RF Transistors (e.g., HEMTs): Diamond’s high thermal conductivity (significantly better than sapphire or SiC) allows InN-based devices to operate at higher power densities and frequencies without overheating, improving reliability and performance.
  • Optoelectronics and Sensing:
    • Near-Infrared Detectors: InN’s narrow bandgap (~0.7 eV) enables detection in the near-infrared spectrum, specifically targeting the 1.55 ”m optical communication band.
    • High-Efficiency Solar Cells: InN is a key component in InGaN and InAlN ternary alloys, which can tune the bandgap to cover the entire visible light spectrum, leading to highly efficient, full-spectrum photovoltaic devices.
  • Solid-State Lighting:
    • Advanced LEDs: InN-based alloys are essential for designing various colored light-emitting diodes, expanding the range of available wavelengths beyond traditional GaN/AlN systems.
  • Advanced Substrate Technology:
    • Thermal Management Platforms: The successful integration of InN on self-standing diamond validates a platform for other high-power semiconductor materials (like GaN) that require extreme heat dissipation capabilities.
View Original Abstract

The progress of InN semiconductors is still in its infancy compared to GaN-based devices and materials. Herein, InN thin films were grown on self-standing diamond substrates using low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) with inert N2 used as a nitrogen source. The thermal conductivity of diamond substrates makes the as-grown InN films especially attractive for various optoelectronic applications. Structural and electrical properties which depend on deposition temperature were systematically investigated by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Hall effect measurement. The results indicated that the quality and properties of InN films were significantly influenced by the deposition temperature, and InN films with highly c-axis preferential orientation and surface morphology were obtained at optimized temperatures of 400 °C. Moreover, their electrical properties with deposition temperature were studied, and their tendency was correlated with the dependence on micro- structure and morphology.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1998 - AIN heteroepitaxial and oriented films grown on (111), (110) and (100) natural diamond faces [Crossref]
  2. 2009 - Growth of GaN on nano-crystalline diamond substrates [Crossref]
  3. 2011 - Realising epitaxial growth of GaN on (001) diamond [Crossref]
  4. 2009 - GaN grown on (111) single crystal diamond substrate by molecular beam epitaxy [Crossref]
  5. 2020 - GaN-on-diamond technology platform: Bonding-free membrane manufacturing process [Crossref]
  6. 2020 - Integration of GaN and diamond using epitaxial lateral overgrowth [Crossref]
  7. 2020 - Theoretical prediction of electronic and optical properties of haft-hydrogenated InN monolayers [Crossref]
  8. 2019 - Tree-like structures of InN nanoparticles on agminated anodic aluminum oxide by plasma-assisted reactive evaporation [Crossref]
  9. 2019 - Tuning the electronic, photocatalytic and optical properties of hydrogenated InN monolayer by biaxial strain and electric field [Crossref]

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