Fabrication of p-Type ZnO -N Films by Oxidizing Zn3N2 Films in Oxygen Plasma at Low Temperature

At a Glance

Metadata	Details
Publication Date	2017-02-27
Journal	Materials
Authors	Yuping Jin, Nuannuan Zhang, Bin Zhang
Institutions	Institute of Modern Physics, Fudan University
Citations	11
Analysis	Full AI Review Included

Technical Documentation & Analysis: Low-Temperature p-Type ZnO:N Fabrication

This document analyzes the research paper “Fabrication of p-Type ZnO:N Films by Oxidizing Zn₃N₂ Films in Oxygen Plasma at Low Temperature” and connects the findings to 6CCVD’s advanced material capabilities, specifically focusing on high-performance diamond solutions for next-generation optoelectronics.

Executive Summary

The research successfully demonstrates a low-temperature method for fabricating high-quality p-type ZnO:N films, a critical step for flexible and transparent optoelectronic devices.

Core Achievement: Successful preparation of p-type ZnO:N films by oxidizing Zn₃N₂ films using oxygen plasma at temperatures ranging from Room Temperature (RT) to 300 °C.
Highest Performance: The film oxidized at RT exhibited the highest hole concentration (6.22 x 10¹⁸ cm^-3) and the lowest resistivity (39.47 Ω·cm).
Defect Engineering: The use of high-energy oxygen plasma significantly reduced the concentration of Oxygen Vacancy (V₀) defects, which typically compensate acceptor dopants in p-type ZnO.
Optimal Processing: The film oxidized at 200 °C showed the lowest V₀ defect concentration and the strongest UV emission, indicating optimal optical quality.
Material Transformation: XRD and non-RBS confirmed the complete transformation of the Zn₃N₂ phase into the hexagonal wurtzite ZnO phase, even at RT oxidation.
Application Relevance: This low-temperature process is highly significant for developing ZnO-based optoelectronic devices, especially those requiring temperature-sensitive plastic substrates.

Technical Specifications

The following hard data points were extracted from the characterization of the oxidized ZnO:N films:

Parameter	Value	Unit	Context
Highest Hole Concentration	6.22 x 10¹⁸	cm^-3	Achieved at RT oxidation (2-RT sample)
Lowest Resistivity	39.47	Ω·cm	Achieved at RT oxidation (2-RT sample)
Hall Mobility (2-RT sample)	0.03	cm²·V^-1·s^-1	Measured in the dark at 0.35 T
Optimal V₀ Reduction Temperature	200	°C	Yielded lowest V₀ defects and strongest UV emission
Film Thickness (Oxidized ZnO:N)	~120	nm	Measured by non-Rutherford backscattering (non-RBS)
Oxidation Temperature Range	RT to 400	°C	Processing window for p-type conversion
Conduction Type Transition	400	°C	p-type converted back to n-type conduction
ZnO Band Gap (RT)	3.37	eV	Wide band gap semiconductor property

Key Methodologies

The experiment involved two primary steps: Zn₃N₂ film deposition via sputtering and subsequent oxidation via plasma enhanced chemical vapor deposition (PECVD).

1. Zn₃N₂ Film Preparation (RF Reactive Magnetron Sputtering)

Substrate Material: Quartz.
Target Material: Zinc disk (99.999%).
Process Gases: Ar (99.999%) and N₂ (99.999%).
Gas Flow Rate: 30 SCCM (for both Ar and N₂).
Sputtering Power: 40 W.
Working Pressure: 5 Pa.
Deposition Time: 30 minutes.
Substrate Temperatures Used: 200 °C and Room Temperature (RT).

2. Oxidizing Process (PECVD)

System: Plasma Enhanced Chemical Vapor Deposition (PECVD).
Background Vacuum: Better than 2 x 10^-5 mbar.
Oxidizing Gas: O₂ (99.999%).
O₂ Flow Rate: 9.5 SCCM.
RF Power: 100 W.
Working Pressure: 400 mtorr.
Oxidation Temperature Range: Varied from RT to 400 °C.
Oxidation Time: 2 hours.

3. Characterization Techniques

Structural: X-ray Diffraction (XRD) using Cu Kα radiation (λ = 1.54060 Å).
Composition/Thickness: Non-Rutherford Backscattering (non-RBS).
Chemical States: High-resolution X-ray Photoelectron Spectroscopy (XPS), calibrated using the C 1s line at 284.8 eV.
Electrical: Hall-effect measurement (ACCENT HL5500PC) using Van der Pauw configuration and 0.35 T magnetic field.
Optical: Photoluminescence (PL) using a He-Cd laser source (325 nm wavelength).

6CCVD Solutions & Capabilities

The research highlights the challenges of achieving stable, high-quality p-type doping and defect control (V₀ reduction) in wide bandgap semiconductors like ZnO for optoelectronic applications. While ZnO is a promising material, MPCVD Diamond offers superior intrinsic properties—including the widest bandgap, highest thermal conductivity, and chemical inertness—making it the ideal material for high-power, high-frequency, and extreme environment optoelectronics.

6CCVD provides the necessary advanced diamond materials and engineering services to replicate, extend, or surpass the performance demonstrated in this research.

Applicable Materials for Advanced Optoelectronics

Material Grade	Description & Relevance to Research	Key 6CCVD Advantage
Boron-Doped Diamond (BDD)	P-type Analog: BDD is the ultimate p-type wide bandgap semiconductor. It provides stable, high-concentration p-type conductivity (up to 10²¹ cm^-3) without the complex defect compensation issues (like V₀) inherent in ZnO. Ideal for high-power UV LEDs, detectors, and high-frequency devices.	Stable, high-concentration p-type doping; extreme thermal management (k > 2000 W/mK).
Optical Grade Single Crystal Diamond (SCD)	UV Transparency & Substrate: SCD is highly transparent across the UV spectrum (including the 380 nm UV emission noted in the paper). It serves as an ideal, defect-free substrate for epitaxial growth of other wide bandgap materials (e.g., GaN, AlN, or even ZnO) where superior thermal extraction is required.	Exceptional UV transparency; Ra < 1 nm polishing for perfect thin-film epitaxy.
Polycrystalline Diamond (PCD)	Large Area & Cost Efficiency: For large-area flexible or transparent electronics where the high cost of SCD is prohibitive, high-quality PCD wafers offer excellent thermal and mechanical properties.	Wafers up to 125 mm diameter; excellent thermal spreading capability.

Customization Potential for Device Integration

6CCVD’s in-house manufacturing capabilities directly address the needs of advanced thin-film device fabrication, such as those described in the paper:

Custom Dimensions: While the paper used small pieces cut from sputtered films, 6CCVD supplies SCD and PCD wafers/plates in custom dimensions up to 125 mm (PCD) and thicknesses up to 10 mm (Substrates), ensuring compatibility with standard semiconductor processing lines.
Precision Polishing: Achieving high-quality thin films (like the ZnO:N) requires ultra-smooth substrates. 6CCVD guarantees Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, providing the necessary surface quality for subsequent deposition processes (sputtering, PECVD, or epitaxy).
Integrated Metalization: The researchers used Indium (In) electrodes for Hall measurements. 6CCVD offers comprehensive, in-house metalization services, including deposition of standard Ohmic and Schottky contacts (Au, Pt, Pd, Ti, W, Cu) tailored for wide bandgap semiconductor devices.

Engineering Support

The successful fabrication of p-type ZnO:N relied heavily on defect control and low-temperature processing. 6CCVD’s in-house PhD team specializes in the defect engineering and doping of wide bandgap materials.

Defect Control Consultation: We offer expert consultation on material selection and processing parameters for projects requiring precise control over point defects (analogous to V₀ reduction) and substitutional doping in wide bandgap systems.
Thermal Management Solutions: For high-power optoelectronic devices (like UV LEDs or lasers) where thermal management is critical—a limitation often faced by ZnO on plastic substrates—6CCVD can design and supply diamond heat spreaders and substrates that maximize device lifetime and efficiency.
Global Supply Chain: We ensure reliable global shipping (DDU default, DDP available) of highly sensitive, custom-engineered diamond materials.

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

View Original Abstract

The oxygen vacancy (VO) is known as the main compensation center in p-type ZnO, which leads to the difficulty of fabricating high-quality p-type ZnO. To reduce the oxygen vacancies, we oxidized Zn3N2 films in oxygen plasma and successfully prepared p-type ZnO:N films at temperatures ranging from room temperature to 300 °C. The films were characterized by X-ray diffraction (XRD), non-Rutherford backscattering (non-RBS) spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectrum, and Hall Effect. The results show that the nitrogen atoms successfully substitute the oxygen sites in the ZnO:N films. The film prepared at room temperature exhibits the highest hole concentration of 6.22 × 1018 cm−3, and the lowest resistivity of 39.47 Ω∙cm. In all ZnO:N films, the VO defects are reduced significantly. At 200 °C, the film holds the lowest value of VO defects and the strongest UV emission. These results imply that oxygen plasma is very efficient in reducing VO defects in p-type ZnO:N films, and could greatly reduce the reaction temperature. This method is significant for the development of ZnO-based optoelectronic devices.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma10030236

References

2005 - Fully transparent ZnO thin-film transistor produced at room temperature [Crossref]
2005 - Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO [Crossref]
2009 - Fundamentals of zinc oxide as a semiconductor [Crossref]
2012 - Oxide semiconductor thin-film transistors: A review of recent advances [Crossref]
2014 - 25th Anniversary article: Organic field-effect transistors: The path beyond amorphous silicon [Crossref]
2002 - Hydrogen: A relevant shallow donor in zinc oxide [Crossref]
2000 - Hydrogen as a cause of doping in zinc oxide [Crossref]
2007 - Native point defects in ZnO [Crossref]
1983 - Deep energy levels of defects in the wurtzite semiconductors AIN, CdS, CdSe, ZnS, and ZnO [Crossref]
2003 - Optical properties and electrical characterization of p-type ZnO thin films prepared by thermally oxiding Zn3N2 thin films [Crossref]