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.

APU MISTRY

ANUP GORAI

DIPANKAR 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.

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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.

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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

Optical and Quantum Electronics

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

Optik

Advantages of InGaN/InGaN quantum well light emitting diodes: Better electron-hole overlap and stable output

A hurdle encountered in the InGaN/GaN LED, is, that the overlap of electrons and holes decreases significantly under certain conditions which deteriorates the performance of the LED. Several methods are being studied for increasing the overlap of electrons and holes of which introduction of a staggered InGaN/GaN QW, in place of the rectangular QW seems promising. In this paper we have studied comprehensively, different forms of the staggered QW; single sided and symmetric, with different Indium compositions in the well. Computations have been carried out through the self-consistent solutions of Schrödinger and Poison equations. We have studied the band structures, fields, the carrier distributions, the transition energies and the overlap of the electron and hole wave functions with current densities. It has been found that the overlap of electrons and holes increases significantly for the staggered QWs at the same current. The best results are obtained for the symmetrically staggered QWs, where the overlap increases even up to three times that of the rectangular QW and using this structure the operating current may be decreased by more than two orders of magnitude to obtain the same transition energy. The theoretical and computational results will be presented with suitable discussions. © 2017 Elsevier B.V.

Optical Materials

Constructive and comprehensive studies on the advantages of using staggered InxGa1-xN/InyGa1-yN QWs in LEDs

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

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.

Calculations for the band lineup of strained Inx Ga1-x N/GaN quantum wells: Effects of strain on the band offsets

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

Journal	Data powered by TypesetOptical and Quantum Electronics
Publisher	Data powered by TypesetSPRINGER
ISSN	0306-8919