Tunnel-injected sub-260 nm ultraviolet light emitting diodes

Zhang, Y.; Krishnamoorthy, Sriram; Akyol, Fatih; Bajaj, Sanyam; Allerman, Andrew A.; Moseley, Michael William; Armstrong, Andrew M.; Rajan, Siddharth

doi:10.1063/1.4983352

Cited by 60 publications

(46 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Up to date, great progress has been made on the UVC light‐emitting diodes (LEDs) by using active regions of AlGaN multiple quantum wells (MQWs) . However, the optical output power of current UVC LEDs drops significantly as the light emission wavelength gets shorter. Those LEDs suffer from poor hole injection efficiency in high‐Al‐content p‐type AlGaN, low internal quantum efficiency (IQE) caused by large‐lattice‐mismatch heteroepitaxy, and strong quantum‐confined Stark effect (QCSE), as well as the absorption by the nontransparent GaN contact layers …”

mentioning

confidence: 99%

Deep Ultraviolet Light Source from Ultrathin GaN/AlN MQW Structures with Output Power Over 2 Watt

Wang

Rong

Иванов

et al. 2019

Advanced Optical Materials

View full text Add to dashboard Cite

which are environmentally friendly and enable portability and high efficiency. Up to date, great progress has been made on the UVC light-emitting diodes (LEDs) by using active regions of AlGaN multiple quantum wells (MQWs) .[8-14] However, the optical output power of current UVC LEDs drops significantly as the light emission wavelength gets shorter. Those LEDs suffer from poor hole injection efficiency in high-Al-content p-type AlGaN, low internal quantum efficiency (IQE) caused by large-lattice-mismatch heteroepitaxy, and strong quantum-confined Stark effect (QCSE), as well as the absorption by the nontransparent GaN contact layers. [15][16][17] A promising approach that dramatically improves the light output power is electron-beam (e-beam) pumping, especially for the short-wavelength UVC spectral range. [3,[18][19][20][21][22][23][24] This approach allows one to bypass the need for p-type or n-type injection layers and, thus, can largely increase the carrier injection efficiency. This provides a unique advantage over conventional LEDs at UVC range, since the p-type doping for high-Al-content AlGaN is High-output-power electron-beam (e-beam) pumped deep ultraviolet (DUV) light sources, operating at 230-270 nm, are achieved by adjusting the well thickness of binary ultrathin GaN/AlN multiple quantum wells. These structures are fabricated on high-quality thermally annealed AlN templates by metal-organic chemical vapor deposition. Owing to the reduced dislocation density, large electron-hole overlap, and efficient carrier injection by e-beam, the DUV light sources demonstrate high output powers of 24.8, 122.5, and 178.8 mW at central wavelengths of 232, 244, and 267 nm, respectively. Further growth optimization and employing an e-gun with increased beam current lead to a record output power of ≈2.2 W at emission wavelength of ≈260 nm, the key wavelength for water sterilization. This work manifests the practical levels of high-output-power DUV light sources operated by using e-beam pumping method. The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201801763.Solid-state deep ultraviolet (DUV) optoelectronic devices in the spectral range of 200-280 nm, i.e., ultraviolet-C (UVC), have attracted much attention for their wide applications in sterilization, medical treatment, security, solar-blind photodetection, and so on. [1][2][3][4][5][6][7] Currently, Al(Ga)N material system is the most promising candidate for solid-state UVC light sources

show abstract

mentioning

confidence: 99%

Deep Ultraviolet Light Source from Ultrathin GaN/AlN MQW Structures with Output Power Over 2 Watt

Wang

Rong

Иванов

et al. 2019

Advanced Optical Materials

View full text Add to dashboard Cite

show abstract

“…Another benefit of the tunnel-injected UV LED structure is that holes are injected through interband tunneling, which resists the influence of the extremely low thermal activation rate of Mg acceptors in AlGaN. 17,18 This is critical for deep UV LEDs, as the thermally activated hole concentration decreases significantly with the increasing Al content in the p-AlGaN layer. While conventional UV LEDs have encountered a substantial efficiency reduction when lowering the emission wavelength in the deep UV wavelength range, the tunnel-injected UV LED structure could potently solve the problem and lead to efficient deep UV emitters.…”

mentioning

confidence: 99%

“…9 Tunneling hole injection into p-AlGaN was demonstrated with appreciable light emission in a wide UV wavelength range of 325-257 nm from the tunnel-injected UV LED structure. 9,13,[16][17][18]31 Incorporation of tunnel junctions into nanowire LEDs has also been reported with excellent device performances. 32,33 In this work, we demonstrate efficient deep UV LEDs with an on-wafer peak external quantum a)…”

mentioning

confidence: 99%

Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

Zhang

Jamal-Eddine

Akyol

et al. 2018

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

We report on the high efficiency tunnel-injected ultraviolet light emitting diodes (UV LEDs) emitting at 287 nm. Deep UV LED performance has been limited by the severe internal light absorption in the p-type contact layers and low electrical injection efficiency due to poor p-type conduction. In this work, a polarization engineered Al 0.65 Ga 0.35 N/In 0.2 Ga 0.8 N tunnel junction layer is adopted for nonequilibrium hole injection to replace the conventionally used direct p-type contact. A reverse-graded AlGaN contact layer is further introduced to realize a low resistance contact to the top n-AlGaN layer. This led to the demonstration of a low tunnel junction resistance of 1.9 Â 10 À3 X cm 2 obtained at 1 kA/cm 2. Light emission at 287 nm with an on-wafer peak external quantum efficiency of 2.8% and a wall-plug efficiency of 1.1% was achieved. The measured power density at 1 kA/cm 2 was 54.4 W/cm 2 , confirming the efficient hole injection through interband tunneling. With the benefits of the minimized internal absorption and efficient hole injection, a tunnel-injected UV LED structure could enable future high efficiency UV emitters.

show abstract

“…Simple approaches of the reflective p-contact did not lead to a practical solution. Attempts to solve the problem by inserting a thin InGaN layer [115][116][117], incorporating quantum dots [118], or fabricating nanorods [119] are ongoing. However, major manufacturers currently incorporate a p-GaN contact layer.…”

Section: Transparent P-cladding Layer and Reflective P-contactmentioning

confidence: 99%

A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire

Nagasawa¹,

Hirano²

2018

Applied Sciences

185

111

View full text Add to dashboard Cite

This paper reviews the progress of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs), mainly focusing in the work of the authors’ group. The background to the development of the current device structure on sapphire is described and the reason for using a (0001) sapphire with a miscut angle of 1.0° relative to the m-axis is clarified. Our LEDs incorporate uneven quantum wells (QWs) grown on an AlN template with dense macrosteps. Due to the low threading dislocation density of AlGaN and AlN templates of about 5 × 108/cm2, the number of nonradiative recombination centers is decreased. In addition, the uneven QW show high external quantum efficiency (EQE) and wall-plug efficiency, which are considered to be boosted by the increased internal quantum efficiency (IQE) by enhancing carrier localization adjacent to macrosteps. The achieved LED performance is considered to be sufficient for practical applications. The advantage of the uneven QW is discussed in terms of the EQE and IQE. A DUV-LED die with an output of over 100 mW at 280–300 nm is considered feasible by applying techniques including the encapsulation. In addition, the fundamental achievements of various groups are reviewed for the future improvements of AlGaN-based DUV-LEDs. Finally, the applications of DUV-LEDs are described from an industrial viewpoint. The demonstrations of W/cm2-class irradiation modules are shown for UV curing.

show abstract

Tunnel-injected sub-260 nm ultraviolet light emitting diodes

Cited by 60 publications

References 32 publications

Deep Ultraviolet Light Source from Ultrathin GaN/AlN MQW Structures with Output Power Over 2 Watt

Deep Ultraviolet Light Source from Ultrathin GaN/AlN MQW Structures with Output Power Over 2 Watt

Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire

Contact Info

Product

Resources

About