Toward Bright and Pure Single Photon Emitters at 300 K Based on GaN Quantum Dots on Silicon

Abstract

Quantum dots (QDs) based on III-nitride semiconductors are promising for single photon emission at non-cryogenic temperatures due to their large exciton binding energies. Here, we demonstrate GaN QD single photon emitters operating at 300 K with g (2) (0) = 0.17±0.08 under continuous wave excitation. At this temperature, single photon emission rates up to 6 × 10 6 s −1 are reached while g (2) (0) ≤ 0.5 is maintained. Our results are achieved for GaN QDs embedded in a planar AlN layer grown on silicon, representing a promising pathway for future interlinkage with optical waveguides and cavities. These samples allow exploring the limiting factors to key performance metrics for single photon sources, such as brightness and single photon purity. While high brightness is assured by large exciton binding energies, the single photon purity is mainly affected by the spectral overlap with the biexcitonic emission. Thus, the performance of a GaN QD as a single photon emitter depends on the balance between the emission linewidth and the biexciton binding energy. We identify small GaN QDs with an emission energy in excess of 4.2 eV as promising candidates for future room temperature applications, since the biexciton binding energy becomes comparable to the average emission linewidth of around 55 meV.Quantum dots (QDs) based on III-V semiconductors have attracted a lot of attention for their use as nonclassical light sources, with the single photon source being the simplest and most elemental representative. Such a source of single photons should be as bright as possible, while retaining a high single photon purity [1, 2]. However, key metrics for such QD-based single photon sources are usually achieved at cryogenic temperatures with the seminal In(Ga)As/(Al)GaAs system [3][4][5]. Identifying a material platform that can enable sufficiently performant single photon sources up to room temperature remains a challenging quest. In this respect, the main contenders are point defects in wide-bandgap semiconductors (2D materials [6] and bulk semiconductors [7, 8]), nitrogen and silicon vacancies in diamond [9], as well as semiconductor QDs [10][11][12]. It would be advantageous to employ a material system with high integrability into a suitable photonic environment that offers epitaxial control. In this regard, III-nitrides offer a unique possibility as bipolar doping can be achieved, foreign and homoepitaxial substrates are available, and growth and processing techniques are well established, leading to their widespread implementation at an industrial scale for solid state lighting.III-nitrides have shown promising advances in terms of single photon emission (SPE) by employing GaN/AlN [13,14], GaN/AlGaN [15,16] and InGaN/GaN QDs [17][18][19][20][21]. Furthermore, SPE at temperatures as high as 350 K [22] and two-photon emission up to 50 K [23] have been demonstrated. The progress towards room temperature operation is directly linked to the exciton-phonon coupling. With rising temperature the phonon bath becomes * sebastian.tamariz...

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“…However, a reliable SPE platform with a high signal to noise ratio and relatively low g (2) (0) must be achieved by the growth of high-quality material with a higher emission energy of ~3 eV. Due to the large exciton binding energies of III-nitride semiconductor quantum dots (QDs), they are promising candidates for single-photon emission at noncryogenic temperatures [52].…”

“…It has been reported that GaN QD single-photon emitters can operate at 300 K and their performance for the emission of single photons depends on the balance between the emission line width and the biexciton binding energy [52]. It has been shown that when using GaN QDs embedded in a planar AlN layer, grown on silicon, the brightness and single-photon purity can be adjusted to improve the performance metrics [52]. Authors have described that the large exciton binding energies lead to high brightness and, by the spectral overlap with the biexcitonic emission, this can be used to affect the single-photon purity.…”

“…Authors have described that the large exciton binding energies lead to high brightness and, by the spectral overlap with the biexcitonic emission, this can be used to affect the single-photon purity. They concluded that small GaN QD single-photon emitters can play a significant role in future room temperature applications [52]. Additionally, encouraging progress has been made in the hybrid integration of solid-state SPSs based on InAs/GaAs quantum dots (QDs) [53].…”

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“…Research in wide-bandgap III-nitride semiconductors continues to progress rapidly, especially for the materials with bandgap exceeding that of gallium nitride (3.4 eV). Specifically, III-nitride based heterostructures provide new opportunities for a wide range of research and device applications, such as piezotronics and piezophototronics [1], self-powered photoelectrochemical-type photodetectors [2], room-temperature quantum emitters [3], single photon emitters [4][5][6], resonant tunneling diodes [7], highelectron-mobility transistors [8,9], efficient photoelectrocatalysts for solar water splitting [10], multi-wavelength light-emitting diodes (LEDs) [11,12], and deep ultraviolet (DUV)-LEDs [13][14][15][16][17]. AlGaN-based DUV-LEDs represent a sustainable alternative to replace the environmentally harmful conventional mercury lamps [18] and thus, are becoming crucial for many applications such as water purification and/or inactivation of microorganisms, including bacteria, fungi, and viruses [19,20].…”

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“…In principle, single-photon emission can be obtained in a wide spectral range from medium ultraviolet to the optical telecommunication C-band (1.55 m) through optical pumping of single QDs fabricated in different material systems [ 4 , 5 , 6 , 7 , 8 ]. Most of such emitters operate at cryogenic temperatures and only the epitaxial QDs made of wide-band-gap materials can work as SPE up to room temperature [ 9 , 10 ]. Alternative systems for producing single-photon emission at elevated temperatures could be single molecules [ 11 ], diamond color centers [ 12 ], and colloidal quantum dots [ 13 ].…”