Bright Single-Photon Emitting Diodes Based on the Silicon-Vacancy Center in AlN/Diamond Heterostructures

At a Glance

Metadata	Details
Publication Date	2020-02-19
Journal	Nanomaterials
Authors	Igor A. Khramtsov, Dmitry Yu. Fedyanin
Institutions	Moscow Institute of Physics and Technology
Citations	16
Analysis	Full AI Review Included

Technical Documentation and Analysis: High-Brightness SiV SPEDs via AlN/Diamond Heterostructures

Executive Summary

This research proposes a paradigm shift for electrically driven Single-Photon Emitting Diodes (SPEDs) using a nanoscale n-AlN/i-diamond/p-diamond heterostructure incorporating silicon-vacancy (SiV) centers. The core value proposition is the ability to achieve unprecedented room-temperature single-photon emission rates in a scalable, electrically excited device platform.

Breakthrough Performance: Numerical simulations demonstrate a maximum Single-Photon Electroluminescence (SPEL) rate reaching 3.9 Mcps (Megacounts per second), which is over five times higher than comparable diamond p-i-n diode designs.
Nanoscale Architecture: The proposed device utilizes a thin (300 nm) intrinsic diamond layer, suitable for integration into dense, on-chip nano-optoelectronic circuits required for practical quantum information systems.
Novel Injection Mechanism: Electrons are efficiently injected into the diamond layer from the n-AlN layer via quantum tunneling across a substantial 0.9 eV conduction-band offset (CBO), solving the historical challenge of low n-type diamond free-carrier density.
Material Requirements: Success hinges on the precision growth of high-quality intrinsic diamond layers with tailored thickness (0.3 µm) and highly doped p-type diamond substrates (N_a = 10¹⁸ cm^-3).
Scalability and Robustness: The high SPEL rate is projected to be robust against interface defects (up to 10¹⁰ cm^-2) at high bias, confirming the viability of the AlN/diamond structure for manufacturing.
Future Potential: Theoretical maximum SPEL rates exceeding 40 Mcps are predicted if quantum efficiency (QE) and shelving state lifetime are optimized, suggesting significant headroom for future material development.

Technical Specifications

The following parameters define the simulated performance and critical structural elements of the AlN/Diamond SPED.

Parameter	Value	Unit	Context
Material Structure	n-AlN/i-Diamond/p-Diamond	N/A	Heterojunction SPED utilizing SiV color centers.
Maximum SPEL Rate (Simulated)	3.9 x 10⁶	cps	Achieved at high current density (500 A/cm²) assuming 30% QE.
SPEL Rate Multiplier	5x	N/A	Relative performance increase over optimized diamond p-i-n diodes.
Target Application Temperature	Room Temperature	°C	Crucial for scalable quantum technology implementation.
i-Diamond Thickness	300	nm (0.3 µm)	Emitter placement region, ideal for nanoscale integration.
p-Diamond Acceptor Density (N_a)	10¹⁸	cm^-3	Required doping for the substrate region.
n-AlN Donor Density (N_d)	10¹⁸	cm^-3	Electron injection layer doping concentration.
AlN/Diamond Conduction Band Offset (CBO)	0.9	eV	High potential barrier, overcome via tunneling.
Electric Field at Junction (High Bias)	>5 x 10⁶	V/cm	Enables efficient electron tunneling across the barrier (<3 nm width).
SiV Wavelength	~738	nm	Polarized emission, characteristic of the SiV center.
SiV Shelving State Lifetime (T_s)	~100	ns	Limits maximum achievable SPEL rate at high injection.

Key Methodologies

The core design and simulation methodology relies on precisely engineered layers and utilizes quantum mechanical effects to achieve efficient carrier injection.

Heterostructure Definition: The device structure was defined as a vertical n-AlN/i-diamond/p-diamond stack, with the SiV color center positioned within the intrinsic (i) diamond layer.
Layer Thickness Specification: The i-diamond region was fixed at 300 nm (0.3 µm) to achieve nanoscale device dimensions, while the p-diamond substrate thickness was set to 2 µm.
Doping Control: High doping concentrations (10¹⁸ cm^-3) were specified for both the n-AlN and p-diamond regions to maximize carrier reservoirs.
Interface Modeling: The critical AlN/diamond interface was modeled with a large 0.9 eV CBO (C-N polarity, worst-case scenario) to analyze the efficiency of carrier transport mechanisms.
Tunneling Current Simulation: The electron current density (J) across the heterojunction was modeled primarily via quantum mechanical tunneling (Equation 2), given the high potential barrier prevents efficient thermionic emission at room temperature.
2D Self-Consistent Numerical Simulation: All electronic and optical parameters (carrier densities, current flow, and SPEL rates) were computed using commercial software (Atlas Silvaco) to ensure a realistic 2D, self-consistent evaluation of transport phenomena under forward bias (up to 6.5 V).

6CCVD Solutions & Capabilities

This innovative AlN/diamond SPED design requires materials with extreme precision in purity, doping, and surface quality—exactly the core expertise of 6CCVD’s MPCVD diamond services. Replicating or extending this research into working prototypes mandates stringent control over the diamond feedstock and processing.

Applicable Materials

To replicate the n-AlN/i-diamond/p-diamond SPED, researchers require the following specific materials, available custom-grown by 6CCVD:

Intrinsic/Doped Layer (i-Diamond): Optical Grade SCD Wafers.
- Requirement: Ultra-high purity, intrinsic diamond is essential for controlled SiV center incorporation and minimizing competing non-radiative recombination pathways.
- 6CCVD Capability: We provide Single Crystal Diamond (SCD) material with thicknesses precisely controlled from 0.1 µm up to 500 µm, perfectly accommodating the required 300 nm (0.3 µm) i-region definition.
Substrate (p-Diamond): Heavy Boron-Doped (BDD) Substrates.
- Requirement: The substrate requires a high acceptor density (N_a = 10¹⁸ cm^-3) to ensure efficient hole injection.
- 6CCVD Capability: We specialize in controlled Boron Doping, capable of delivering highly conductive BDD substrates to meet or exceed the required 10¹⁸ cm^-3 doping concentration.

Customization Potential for Nano-Optoelectronics

Achieving high-performance single-photon emission depends critically on interfacing high-quality diamond layers with secondary materials (AlN) and creating stable electrical contacts.

Service Requirement (From Paper)	6CCVD Engineering Solution	Impact on Research
Layer Thickness Control (300 nm)	Precision growth of SCD down to 0.1 µm.	Ensures the high electric field and tunneling required for efficient injection in nanoscale devices.
Interface Quality (AlN/Diamond)	Superior Polishing: SCD surface roughness Ra < 1 nm.	Critical for minimizing defects at the AlN/Diamond interface that limit SPEL brightness (as discussed in Figure 6 analysis).
Electrical Contact Implementation	Custom Metalization Services: Au, Pt, Pd, Ti, W, Cu.	Allows researchers to create robust, low-resistance ohmic contacts on the p-diamond and subsequently pattern contacts for device operation.
Large-Area Scalability	Large-Format Diamond Wafers: Plates/wafers up to 125 mm (PCD).	Enables large-scale prototyping and batch processing of SPED arrays for integrated quantum circuits.

Engineering Support

The viability of this technology relies on mitigating factors like lattice mismatch between AlN and diamond and controlling interface defects. 6CCVD’s in-house PhD team specializes in MPCVD growth optimization and material characterization. We offer expert consultation on:

Material Selection: Guiding researchers on the optimal crystal orientation (e.g., (111) vs. (100)) and doping concentration for electrically driven SiV projects.
Interface Preparation: Advising on advanced polishing and surface termination (e.g., Oxygen passivation, referenced in the paper) to reduce interface defect density and potentially lower the CBO barrier (0.9 eV to 0.4 eV regime).
SiV Incorporation: Assisting in the controlled incorporation of silicon during MPCVD growth to achieve optimal density and location of SiV centers within the intrinsic layer.

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

View Original Abstract

Practical implementation of many quantum information and sensing technologies relies on the ability to efficiently generate and manipulate single-photon photons under ambient conditions. Color centers in diamond, such as the silicon-vacancy (SiV) center, have recently emerged as extremely attractive single-photon emitters for room temperature applications. However, diamond is a material at the interface between insulators and semiconductors. Therefore, it is extremely difficult to excite color centers electrically and consequently develop bright and efficient electrically driven single-photon sources. Here, using a comprehensive theoretical approach, we propose and numerically demonstrate a concept of a single-photon emitting diode (SPED) based on a SiV center in a nanoscale AlN/diamond heterojunction device. We find that in spite of the high potential barrier for electrons in AlN at the AlN/diamond heterojunction, under forward bias, electrons can be efficiently injected from AlN into the i-type diamond region of the n-AlN/i-diamond/p-diamond heterostructure, which ensures bright single-photon electroluminescence (SPEL) of the SiV center located in the i-type diamond region. The maximum SPEL rate is more than five times higher than what can be achieved in SPEDs based on diamond p-i-n diodes. Despite the high density of defects at the AlN/diamond interface, the SPEL rate can reach about 4 Mcps, which coincides with the limit imposed by the quantum efficiency and the lifetime of the shelving state of the SiV center. These findings provide new insights into the development of bright room-temperature electrically driven single-photon sources for quantum information technologies and, we believe, stimulate further research in this area.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano10020361

References

2015 - Electrically Driven Quantum Light Sources [Crossref]
2012 - Engineered quantum dot single-photon sources [Crossref]
2011 - Diamond-based single-photon emitters [Crossref]
2016 - Quantum nanophotonics in diamond [Crossref]
2019 - Quantum nanophotonics with group IV defects in diamond [Crossref]
2015 - Robust luminescence of the silicon-vacancy center in diamond at high temperatures [Crossref]
2014 - Multiple intrinsically identical single-photon emitters in the solid state [Crossref]
2016 - Ultrabright single-photon source on diamond with electrical pumping at room and high temperatures [Crossref]
2019 - Superinjection in Diamond p-i-n Diodes: Bright Single-Photon Electroluminescence of Color Centers Beyond the Doping Limit [Crossref]