Multijunction GaInN-based solar cells using a tunnel junction

Kurokawa, Haruhisa; Kaga, Mitsuru; Goda, Tomomi; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi

doi:10.7567/apex.7.034104

Cited by 23 publications

(15 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, technological progress in III-nitride based wide bandgap semiconductors has been greatly encouraged because of a continuous demand for energy saving, long lifetime, and environmentally friendly devices [1][2][3]. Since the bandgap of GaInN ternary alloys covers a broad spectral range, from visible to ultra-violet, these materials are suitable for optoelectronic devices such as light-emitting diodes (LEDs), laser diodes, solar-cells, and photo-detectors (PDs) [4][5][6][7]. III-nitride based semiconductors are typically grown on sapphire substrates by using metal-organic chemical vapor deposition (MOCVD) because homo-epitaxial substrates are still expensive due to a difficulty in mass production.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Device Performance of GaInN-Based Green Light-Emitting Diode with Sputtered AlN Buffer Layer

et al. 2019

Self Cite

View full text Add to dashboard Cite

In this study, we compared the device performance of GaInN-based green LEDs grown on c-plane sapphire substrates with a conventional low temperature GaN buffer layer to those with a sputtered-AlN buffer layer. The light output power and leakage current characteristics were significantly improved by just replacing the buffer layer with a sputtered-AlN layer. To understand the origin of the improvement in performance, the electrical and optical properties were compared by means of electro-reflectance spectroscopy, I–V curves, electroluminescence spectra, L–I curves, and internal quantum efficiencies. From the analysis of the results, we concluded that the improvement is mainly due to the mitigation of strain and reduction of the piezoelectric field in the multiple quantum wells active region.

show abstract

Section: Introductionmentioning

confidence: 99%

Enhanced Device Performance of GaInN-Based Green Light-Emitting Diode with Sputtered AlN Buffer Layer

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…[10][11][12][13] We replaced the direct p-type contact using an interband tunneling contact by taking advantage of the polarization properties of III-Nitride material. [14][15][16][17][18][19] This minimizes internal light absorption caused by the p-GaN and p-type metal contact layers, and at the same time increases the hole injection efficiency. [10][11][12][13] Using this tunnel-injected UV LED structure, we have demonstrated efficient UV light emission at 325 nm with an on-wafer external quantum efficiency of 3.37%.…”

mentioning

confidence: 99%

Tunnel-injected sub-260 nm ultraviolet light emitting diodes

Zhang

Krishnamoorthy

Akyol

et al. 2017

Applied Physics Letters

View full text Add to dashboard Cite

We report on tunnel-injected deep ultraviolet light emitting diodes (UV LEDs) configured with a polarization engineered Al 0.75 Ga 0.25 N/ In 0.25 Ga 0.75 N tunnel junction structure. Tunnel-injected UV LED structure enables n-type contacts for both bottom and top contact layers. However, achieving Ohmic contact to wide bandgap n-AlGaN layers is challenging and typically requires high temperature contact metal annealing. In this work, we adopted a compositionally graded top contact layer for non-alloyed metal contact, and obtained a low contact resistance of ρ c =4.8×10 -5 Ω cm 2 on n-Al 0.75 Ga 0.25 N. We also observed a significant reduction in the forward operation voltage from 30.9 V to 19.2 V at 1 kA/cm 2 by increasing the Mg doping concentration from 6.2×10 18 cm -3 to 1.5×10 19 cm -3 . Non-equilibrium hole injection into wide bandgap Al 0.75 Ga 0.25 N with E g >5.2 eV was confirmed by light emission at 257 nm.This work demonstrates the feasibility of tunneling hole injection into deep UV LEDs, and provides a novel structural design towards high power deep-UV emitters.

show abstract

“…2(a)). [16][17][18][19][20][21][22] Due to the polarization discontinuity, sheet charges with density over 10 13 cm -2 are induced at the AlGaN/InGaN heterointerfaces and this reduces the tunneling barrier to less than 3 nm ( Fig. 2(b)), leading to much higher tunneling probability compared to the homojunction tunnel junction.…”

mentioning

confidence: 99%

Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

Zhang

Krishnamoorthy

Akyol

et al. 2016

Applied Physics Letters

View full text Add to dashboard Cite

Ultra violet light emitting diodes (UV LEDs) face critical limitations in both the injection efficiency and light extraction efficiency due to the resistive and absorbing p-type contact layers. In this work, we investigate the design and application of polarization engineered tunnel junctions for ultra-wide bandgap AlGaN (Al mole fraction > 50%) materials towards highly efficient UV LEDs. We demonstrate that polarization-induced 3D charge is beneficial in reducing tunneling barriers especially for high composition AlGaN tunnel junctions. The design of graded tunnel junction structures could lead to low tunneling resistance below 10 -3 Ω cm 2 and low voltage consumption below 1 V (at 1 kA/cm 2 ) for high composition AlGaN tunnel junctions. Experimental demonstration of 292 nm emission was achieved through non-equilibrium hole injection into wide bandgap materials with bandgap energy larger than 4.7 eV, and detailed modeling of tunnel junctions shows that they can be engineered to have low resistance, and can enable efficient emitters in the UV-C wavelength range.a) Authors to whom correspondence should be addressed. Electronic mail: zhang.3789@osu.edu, rajan@ece.osu.edu 2The large range of direct bandgaps in the III-Nitride system makes these semiconductors uniquely suitable for achieving ultra violet emission over a wide wavelength range down to 210 nm. III-Nitride ultra-violet light emitting diodes (UV LEDs) have a large variety of applications including water purification and air disinfection, and they provide distinct advantages over traditional gas-based lamps. We propose an approach to realize highly efficient hole injection based on interband tunneling. In this approach, a transparent n-type AlGaN layer is connected to the p-AlGaN layer using an interband tunnel junction ( Fig. 1(b)). Non-equilibrium tunneling injection of holes overcomes limits imposed by thermal ionization of deep acceptors. 9,10 At the same time, it leads to efficient light extraction since it eliminates absorbing p-type top contact layers. 11Making efficient interband p-n tunnel junctions is challenging for ultra-wide bandgap AlGaN materials due to the large band gap, wide depletion barrier, and doping limitations. In this work, we show that nanoscale heterostructure and polarization engineering of tunnel junctions can enable highly efficient tunneling even for ultra-wide bandgap materials where ordinary dopant-based homojunctions would have very low tunneling current density. In this letter, we discuss the design of AlGaN tunnel junctions over the entire Al composition range. We then experimentally demonstrate highly efficient tunnel junctions for AlGaN with Al composition greater than 50%. was used for tunneling probability calculation, and tunneling current was calculated by considering all possible contributions by carriers with different energies. Bandtail states and bandgap narrowing effect due to heavy impurity doping are not included in the simulations, though they could lead to increase in the tunneling probability. ...

show abstract

Multijunction GaInN-based solar cells using a tunnel junction

Cited by 23 publications

References 28 publications

Enhanced Device Performance of GaInN-Based Green Light-Emitting Diode with Sputtered AlN Buffer Layer

Enhanced Device Performance of GaInN-Based Green Light-Emitting Diode with Sputtered AlN Buffer Layer

Tunnel-injected sub-260 nm ultraviolet light emitting diodes

Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions

Contact Info

Product

Resources

About