Enhanced Photoluminescence and Electrical Properties of n-Al-Doped ZnO Nanorods/p-B-Doped Diamond Heterojunction

At a Glance

Metadata	Details
Publication Date	2022-03-30
Journal	International Journal of Molecular Sciences
Authors	Yu Yao, Dandan Sang, Liangrui Zou, Dong Zhang, Qingru Wang
Institutions	Liaocheng University, Changchun University of Technology
Citations	11
Analysis	Full AI Review Included

Technical Documentation & Analysis: Enhanced Diamond Heterojunctions

Executive Summary

This research demonstrates a significant advancement in diamond-based optoelectronics by fabricating an n-Al:ZnO Nanorods/p-B-Doped Diamond (n-Al:ZnO NRs/p-BDD) heterojunction using a hydrothermal approach on a BDD substrate. The results confirm that Al doping drastically enhances both the electrical and photoluminescent properties, positioning BDD as a critical material for next-generation high-temperature devices.

Performance Leap: Al doping resulted in a rectification ratio of 838 at 5 V, a 40-fold improvement over the undoped ZnO/BDD device (19.3).
Low Power Operation: Achieved an ultra-low turn-on voltage of 0.27 V, significantly improving carrier injection efficiency compared to the undoped device (3.4 V).
Enhanced Optical Output: The device exhibited a significant increase in photoluminescence (PL) intensity and a blue shift of the UV emission peak (390 nm to 382 nm).
WLED Candidate: Chromaticity coordinates (0.2957, 0.2907) are close to the standard white light region, making this structure an excellent candidate for high-temperature resistant White Light-Emitting Diodes (WLEDs).
Material Requirement: The core enabling material is the highly conductive, p-type Boron-Doped Diamond (BDD) film, which 6CCVD specializes in producing via high-purity MPCVD.

Technical Specifications

Parameter	Value	Unit	Context
Rectification Ratio	838	N/A	At 5 V (n-Al:ZnO NRs/p-BDD)
Turn-on Voltage (V_on)	0.27	V	Minimum forward voltage
Forward Current (I_F)	67.5	mA	At 5 V (1300x higher than undoped)
Reverse Leakage Current (I_R)	0.077	µA	At -5 V
Ideality Factor (n)	6.8	N/A	Deviation from ideal diode behavior
Barrier Height (Φ_B)	0.55	eV	n-Al:ZnO NRs/p-BDD heterojunction
BDD Carrier Concentration	3.8 x 10¹⁷	cm^-3	Extracted from Hall measurements
BDD Resistivity	0.33	Ω cm	Extracted from Hall measurements
BDD Mobility	48.9	cm² V^-1 s^-1	Extracted from Hall measurements
UV Emission Peak (Shifted)	382	nm	Blue-shifted due to Al doping (Burstein-Moss effect)
BDD Film Thickness (Paper)	~4	µm	Grown on Si substrate
ZnO NR Diameter/Length (Al-Doped)	300 / 1.2	nm / µm	Average dimensions

Key Methodologies

The fabrication of the n-Al:ZnO NRs/p-BDD heterojunction involved precise material synthesis and integration steps:

p-BDD Substrate Preparation:
- Method: Hot Filament Chemical Vapor Deposition (HFCVD) was used to grow p-type BDD films.
- Thickness: Films were grown to a thickness of ~4 µm on Si substrates.
- Doping: Boron doping was incorporated to achieve sufficient conductivity (p-type semiconductor).
n-Al:ZnO Nanorod Growth:
- Method: Hydrothermal approach utilized for the synthesis of n-Al-doped ZnO NRs.
- Precursors: Zinc acetate dihydrate, aluminum nitrate nonahydrate, and anhydrous ethanol were combined in a 0.05 M solution.
- Seed Layer: A ZnO seed layer was transferred to the autoclave liner.
- Growth Conditions: The diamond film with Al:ZnO NRs was removed from the oven after 24 h of treatment at 90 °C.
Device Fabrication and Contacting:
- Structure: The final device structure was Ag/ITO/n-Al:ZnO NRs/p-BDD/Ag.
- Contacts: Two silver conductors were attached as positive and negative electrodes on the conductive surface of the BDD film and ITO glass, confirming ohmic contact characteristics.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality, customizable Boron-Doped Diamond (BDD) materials required to replicate and advance this high-performance heterojunction research for WLED and high-power applications.

Applicable Materials

To replicate the high-conductivity p-type layer essential for this device, 6CCVD recommends:

6CCVD Material	Specification	Relevance to Research
Heavy Boron Doped PCD	Polycrystalline Diamond (PCD) with controlled B doping (p-type).	Ideal for large-area, high-conductivity substrates required for scaling WLEDs and high-power diodes.
Boron Doped SCD	Single Crystal Diamond (SCD) with precise B doping.	Necessary for applications requiring the highest thermal conductivity, minimal defects, and superior crystal quality for fundamental research or high-frequency devices.
Custom Doping Levels	Carrier concentrations precisely controlled up to 10²⁰ cm^-3.	We can match or exceed the 3.8 x 10¹⁷ cm^-3 concentration used in the paper, allowing researchers to optimize device performance further.

Customization Potential

The paper utilized HFCVD-grown BDD films (~4 µm) on Si. 6CCVD’s advanced Microwave Plasma CVD (MPCVD) capabilities offer superior material quality, purity, and dimensional control, enabling direct scaling and optimization:

Substrate Dimensions: While the paper used small films, 6CCVD offers PCD plates/wafers up to 125mm in diameter, crucial for industrial scaling of WLED and optoelectronic devices.
Thickness Control: We provide BDD films with thickness ranging from 0.1 µm up to 500 µm (or substrates up to 10mm), allowing researchers to optimize the depletion layer and thermal management far beyond the constraints of the HFCVD method used in the paper.
Surface Finish: We offer ultra-smooth polishing services (Ra < 5nm for inch-size PCD), which is critical for minimizing interface defects and improving the quality of subsequent nanorod growth (like the Al:ZnO NRs).
Custom Metalization: The device used Ag/ITO contacts. 6CCVD provides in-house metalization services, including Ti, Pt, Au, Pd, W, and Cu, allowing researchers to test optimized ohmic contacts directly on the BDD substrate for improved carrier injection and reduced contact resistance.

Engineering Support

The successful development of the n-Al:ZnO NRs/p-BDD heterojunction relies heavily on minimizing defects and controlling the interface state, which is directly influenced by the quality of the BDD substrate.

Defect Management: 6CCVD’s in-house PhD team specializes in optimizing MPCVD growth recipes to minimize structural defects and residual stresses in BDD films, offering a purer and more stable platform than HFCVD-grown diamond.
Application Expertise: Our engineers can assist with material selection and design consultation for similar high-temperature resistant WLEDs, UV photodetectors, and high-power diode projects, ensuring the BDD substrate meets specific electrical and thermal requirements (e.g., high breakdown voltage, high thermal conductivity).
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) for time-sensitive research projects worldwide.

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

View Original Abstract

The hydrothermal approach has been used to fabricate a heterojunction of n-aluminum-doped ZnO nanorods/p-B-doped diamond (n-Al:ZnO NRs/p-BDD). It exhibits a significant increase in photoluminescence (PL) intensity and a blue shift of the UV emission peak when compared to the n-ZnO NRs/p-BDD heterojunction. The current voltage (I-V) characteristics exhibit excellent rectifying behavior with a high rectification ratio of 838 at 5 V. The n-Al:ZnO NRs/p-BDD heterojunction shows a minimum turn-on voltage (0.27 V) and reverse leakage current (0.077 μA). The forward current of the n-Al:ZnO NRs/p-BDD heterojunction is more than 1300 times than that of the n-ZnO NRs/p-BDD heterojunction at 5 V. The ideality factor and the barrier height of the Al-doped device were found to decrease. The electrical transport behavior and carrier injection process of the n-Al:ZnO NRs/p-BDD heterojunction were analyzed through the equilibrium energy band diagrams and semiconductor theoretical models.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ijms23073831

References

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