Shift of the emission spectrum and the efficiency loss with the operating current are the major challenges in the conventional InGaN/GaN QW LEDs. Several approaches are being tried by different research groups to overcome this hurdle, including, introduction of In in the barriers for which a rigorous study seemed essential. In this paper, our comprehensive and systematic studies on InGaN/InGaN quantum well light emitting diodes reveal that the overlap of electron and hole wave functions can be increased even at low operating currents by the introduction of In in the barriers. The changes of output emission for different In content in the barrier and various doping at different currents are reported, which show that the shift of the energy can be minimized for suitable choice of parameters. The emission and the overlap of electron and hole wave functions have a significant dependence on the doping in the barrier layers which may be used advantageously. Computations have been performed through the self-consistent solutions of Schrödinger and Poisson equations. © 2017 Elsevier GmbH

A GORAI

S PANDA

D BISWAS

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

&nbsp;

The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

&nbsp;

It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Optik

The strong piezoelectric field in the In x Ga 1−x N/GaN quantum well (QW) LEDs, separates the electrons and holes spatially, which decreases the luminescence. Various shapes and compositions of such QWs are studied to improve the performance. We have studied the transition energy (TE), overlap of electron and hole wave functions, band structures and field distributions of the parabolic QWs (PQW) through the self consistent solutions of Schrödinger and Poisson equations. The shape of the PQW is varied along with the compositions and dopings. The square of the overlap of electron and hole wave functions i.e. the transition probability (TP) is strikingly increased, compared to the rectangular QW and it is even higher than the symmetrically staggered QW. At a particular current density, for the same TE, the TP of the PQW increases more than two times that of the rectangular QWs. An important feature, desirable for the QW LEDs emerge. The change of the TE with increase in the current density is minimized. A brief theory, computational procedures and the results will be presented in details with suitable discussions. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Optical and Quantum Electronics

The electronâ€“hole overlap in the parabolic quantum well light emitting diode is much superior to the rectangular: even to that of a staggered quantum well

The strong piezoelectric field in the InxGa1-xN/GaN quantum well (QW) LEDs, separates the electrons and holes spatially, which decreases the luminescence. Various shapes and compositions of such QWs are studied to improve the performance. We have studied the transition energy (TE), overlap of electron and hole wave functions, band structures and field distributions of the parabolic QWs (PQW) through the self consistent solutions of Schrodinger and Poisson equations. The shape of the PQW is varied along with the compositions and dopings. The square of the overlap of electron and hole wave functions i.e. the transition probability (TP) is strikingly increased, compared to the rectangular QW and it is even higher than the symmetrically staggered QW. At a particular current density, for the same TE, the TP of the PQW increases more than two times that of the rectangular QWs. An important feature, desirable for the QW LEDs emerge. The change of the TE with increase in the current density is minimized. A brief theory, computational procedures and the results will be presented in details with suitable discussions.

The electron-hole overlap in the parabolic quantum well light emitting diode is much superior to the rectangular: even to that of a staggered quantum well

The near-infrared spectral region is being used for various fields of applications. Near infrared emitters based on InGaN-ZnSnN2 material systems have not been proposed yet. In this paper, a novel type-II InGaN-ZnSnN2/GaN quantum well (QW) light emitting diode structure is presented for the near-infrared emission. Computations are based on the self-consistent solutions of Schrödinger and Poison equations. In the proposed structure, the emission wavelength (λ) and the overlap of electron and hole wave functions (Meh) are studied with current densities, for different dopings, compositions and well widths of the structure. It is found that the Meh and the radiative efficiency are more than 30% and 40% respectively. The large overlap of electron and hole wavefunctions should make QW light emitting diodes in the near infrared range based on these structures feasible. © 2018 Elsevier B.V.

Optical Materials

Near-infrared light emitting diodes based on the type-II InGaN-ZnSnN2/GaN quantum wells

Several approaches have been tried by researchers for improvement of the InxGa1-xN/GaN QW red LEDs, where due the strong polarization fields, the electron-hole wave functions are separated spatially. In this paper, we have studied the type–II InGaN-ZnSnN2/GaN QW diodes and compared the results with the conventional InGaN/GaN QW diodes for red emission. It reveals that the overlap of electron- hole wave functions are increased more than three times that of the conventional InGaN/GaN QWs. In the active region with lower In-content, hole confinement increases due to higher valance band offset in the type-II structure and the electron-hole wave functions move towards the center of the well. The entire red region of the visible spectrum can be covered with suitable width, position of the ZnSnN2 layer and In content in the InGaN layer. The computations have been carried out through the self-consistent solutions of the Schrödinger and Poisson equations. © 2018 Elsevier Ltd

Materials Science in Semiconductor Processing

Red light emitting diodes based on the type-II InGaN-ZnSnN2/GaN quantum wells

In this paper we have studied comprehensively annealed and non annealed single quantum well (QW) light emitting diode (LED) structures with different doping concentrations in the barriers. Computations have been carried out through the self-consistent solutions of Schrödinger and Poison equations. Wide changes in the transition energies (TE) and the transition probabilities (TP) are observed due to the doping variation. On annealing, with the increase of diffusion length, the results show that depending on the doping concentration, the TE increases monotonically as well as it goes through red-blue shifts. It is also observed that, for lower doping, TP increases and/or decreases with the diffusion length. The variation of TP also depends on the operating current. After a critical doping in the barriers, on annealing, the optical performances of QW LEDs deteriorate. Through change in doping and annealing, the optical performance of the InGaN/GaN QW LEDs may be improved. This information should be of importance to the optoelectronic designer. © 2018

Useful studies on the optical properties of annealed and non annealed InGaN/GaN single QW LEDs, with different dopings in the barrier

The emission spectrum of the conventional InGaN/GaN quantum well (QW) diode changes remarkably with the operating current. The degree of change depends on the constituent parameters of the QW. A detailed investigation has been carried out through the self-consistent solutions of the Schrödinger and Poisson equations to elucidate the change of the emission energy and the transition probability with the operating current and to explore how the changes depend on the well width of the QW and the In mole fraction. It is found that choosing suitable values of the mentioned parameters, the emission energy may be kept almost constant with current, or it may be tuned over a wide range through current. The two possibilities have immense importance for optoelectronic device applications. © 2015 Elsevier GmbH. All rights reserved.

Conspicuous current dependence of the emission energy from InxGa1-xN/GaN quantum well diodes

The effects of the doping level and the operating current on the transition energy of InGaN/GaN QW diodes have been studied through the self-consistent solution of the Schrödinger and Poisson equations. Broad change in the transition energy is observed due to the doping variation. With increase in the current density the emission peak shifts toward higher energy. This shift, which is a major disadvantage of the lighting devices, is reduced significantly by increasing the doping concentration. © 2013 Elsevier Ltd. All rights reserved.

Solid State Communications

Effects of doping concentration on the transition energy of InGaN/GaN quantum well diodes

In the recent years, InGaN/GaN quantum well (QW) light emitting diodes (LEDs) have gathered much importance through the introduction of white LEDs and dual wavelength LEDs. However, the continuous tunability of InGaN/GaN QW LEDs has not been well addressed or discussed. In this paper, we introduce the tunability of an InGaN/GaN QW LED having a well width of 4 nm and In mole fraction of 0.3. The results, obtained from self-consistent solutions of the Schrödinger and Poisson equations, show that the transition energy of the LED may be continuously tuned by the device current. A prominent nonlinearity of the transition energy with the device current is generated, which should be of interest to the research workers in the field of optoelectronics. © 2013 AIP Publishing LLC.

Fulltext

Journal of Applied Physics

Tunability of InGaN/GaN quantum well light emitting diodes through current

Band lineup is one of the most important parameters associated with carrier confinement in heterostructures. Relations for computing the band lineups of Inx Ga1-x N based heterostructures have been developed. The band positions for Inx Ga1-x N/GaN heterointerfaces are calculated from the equations developed, which directly corelate the positions of the bands with the band gap of InN and strain at the interface. The strains are calculated from the In mole fractions and lattice constants. The parameters implicitly involved are the elastic stiffness constants (C11 and C12), the hydrostatic deformation potential of the conduction band (a′), and the hydrostatic deformation potential (a) and shear deformation potential (b) for the valence band. Computations have been carried out for different reported band gaps of InN. The effects of strain become prominent as the mole fraction of In increases, changing the band offset ratio. © 2009 American Institute of Physics.

Journal	Data powered by TypesetOptik
Publisher	Data powered by TypesetElsevier GmbH
ISSN	0030-4026