Superinjection of Holes in Homojunction Diodes Based on Wide-Bandgap Semiconductors

First-Principles Study of High-Pressure Phase Stability and Electron Properties of Be-P Compounds

New, stable stoichiometries in Be-P systems are investigated up to 100 GPa by the CALYPSO structure prediction method. Along with the BeP₂-I4₁/amd structure, we identify two novel compounds of Be₃P₂-P-42₁m and Be₃P₂-C2/m. It should be noted that the Be-P compounds are predicted to be energetically unfavorable above 40 GPa. As can be seen, interesting structures may be experimentally synthesizable at modest pressure. Our results indicate that at 33.2 GPa, the most stable ambient-pressure tetragonal Be₃P₂-P-42₁m transitions to the monoclinic Be₃P₂-C2/m structure. Moreover, the predicted Be₃P₂-P-42₁m and Be₃P₂-C2/m phases are energetically favored compared with the Be₃P₂-Ia-3 structure synthesized experimentally. Electronic structure calculations reveal that BeP₂-I4₁/amd, Be₃P₂-P-42₁m, and Be₃P₂-C2/m are all semiconductors with a narrow band gap. The present findings offer insight and guidance for exploration toward further fundamental understanding and potential applications in the semiconductor field.

Bright Silicon Carbide Single-Photon Emitting Diodes at Low Temperatures: Toward Quantum Photonics Applications

Color centers in silicon carbide have recently emerged as one of the most promising emitters for bright single-photon emitting diodes (SPEDs). It has been shown that, at room temperature, they can emit more than 10⁹ photons per second under electrical excitation. However, the spectral emission properties of color centers in SiC at room temperature are far from ideal. The spectral properties could be significantly improved by decreasing the operating temperature. However, the densities of free charge carriers in SiC rapidly decrease as temperature decreases, which reduces the efficiency of electrical excitation of color centers by many orders of magnitude. Here, we study for the first time the temperature characteristics of SPEDs based on color centers in 4H-SiC. Using a rigorous numerical approach, we demonstrate that although the single-photon electroluminescence rate does rapidly decrease as temperature decreases, it is possible to increase the SPED brightness to 10⁷ photons/s at 100 K using the recently predicted effect of hole superinjection in homojunction p-i-n diodes. This gives the possibility to achieve high brightness and good spectral properties at the same time, which paves the way toward novel quantum photonics applications of electrically driven color centers in silicon carbide.

Single-Photon Sources Based on Novel Color Centers in Silicon Carbide P-I-N Diodes: Combining Theory and Experiment

HIGHLIGHTS

Theory of electrically driven single-photon sources based on color centers in silicon carbide p–i–n diodes. New method of determining the electron and hole capture cross sections by an optically active point defect (color center) from the experimental measurements of the single-photon electroluminescence rate and second-order coherence. The developed method is based on the measurements at the single defect level. Therefore, in contrast to other approaches, one point defect is sufficient to measure its electron and hole capture cross sections.

ABSTRACT

Point defects in the crystal lattice of SiC, known as color centers, have recently emerged as one of the most promising single-photon emitters for non-classical light sources. However, the search for the best color center that satisfies all the requirements of practical applications has only just begun. Many color centers in SiC have been recently discovered but not yet identified. Therefore, it is extremely challenging to understand their optoelectronic properties and evaluate their potential for use in practical single-photon sources. Here, we present a theoretical approach that explains the experiments on single-photon electroluminescence (SPEL) of novel color centers in SiC p–i–n diodes and gives the possibility to engineer highly efficient single-photon emitting diodes based on them. Moreover, we develop a novel method of determining the electron and hole capture cross sections by the color center from experimental measurements of the SPEL rate and second-order coherence. Unlike other methods, the developed approach uses the experimental results at the single defect level that can be easily obtained as soon as a single-color center is identified in the i-type region of the SiC p–i–n diode.

GRAPHIC ABSTRACT

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

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.

Highly Deep Ultraviolet-Transparent h-BN Film Deposited on an Al0.7Ga0.3N Template by Low-Temperature Radio-Frequency Sputtering

Hexagonal boron nitride (h-BN) is an attractive wide-bandgap material for application to emitters and detectors operating in the deep ultraviolet (DUV) spectral region. The optical transmittance of h-BN in the DUV region is particularly important for these devices. We report on the deposition of thick h-BN films (>200 nm) on Al_0.7Ga_0.3N templates via radio-frequency sputtering, along with the realization of ultrahigh transmittance in the DUV region. The fraction of the gas mixture (Ar/N₂) was varied to investigate its effects on the optical transmittance of BN. DUV light transmittance of as high as 94% was achieved at 265 nm. This value could be further enhanced to exceed 98% by a post-annealing treatment at 800 °C in a N₂ ambient for 20 min. The phase of the highly DUV-transparent BN film was determined to be a purely hexagonal structure via Raman spectra measurements. More importantly, these deposition processes were performed at a low temperature (300 °C), which can provide protection from device performance degradation when applied to actual devices.