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Title: Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures

Abstract

The spectra of electroluminescence, photoluminescence, and photocurrent for the In{sub 0.2}Ga{sub 0.8}N/GaN quantum-well structures are studied to clarify the causes for the reduction in quantum efficiency with increasing forward current. It is established that the quantum efficiency decreases as the emitting photon energy approaches the mobility edge in the In{sub 0.2}Ga{sub 0.8}N layer. The mobility edge determined from the photocurrent spectra is E{sub me} = 2.89 eV. At the photon energies hv > 2.69 eV, the charge carriers can tunnel to nonradiative recombination centers with a certain probability, and therefore, the quantum efficiency decreases. The tunnel injection into deep localized states provides the maximum electroluminescence efficiency. This effect is responsible for the origin of the characteristic maximum in the quantum efficiency of the emitting diodes at current densities much lower than the operating densities. Occupation of the deep localized states in the density-of-states 'tails' in InGaN plays a crucial role in the formation of the emission line as well. It is shown that the increase in the quantum efficiency and the 'red' shift of the photoluminescence spectra with the voltage correlate with the changes in the photocurrent and occur due to suppression of the separation of photogenerated carriers in themore » field of the space charge region and to their thermalization to deep local states.« less

Authors:
; ; ; ; ; ;  [1]
  1. Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)
Publication Date:
OSTI Identifier:
21088455
Resource Type:
Journal Article
Resource Relation:
Journal Name: Semiconductors; Journal Volume: 41; Journal Issue: 1; Other Information: DOI: 10.1134/S1063782607010174; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ELECTROLUMINESCENCE; EV RANGE 01-10; GALLIUM NITRIDES; INDIUM NITRIDES; LIGHT EMITTING DIODES; PHOTOLUMINESCENCE; QUANTUM EFFICIENCY; QUANTUM WELLS; SPECTRA

Citation Formats

Bochkareva, N. I., E-mail: n.bochkareva@mail.ioffe.ru, Tarkhin, D. V., Rebane, Yu. T., Gorbunov, R. I., Lelikov, Yu. S., Martynov, I. A., and Shreter, Yu. G. Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures. United States: N. p., 2007. Web. doi:10.1134/S1063782607010174.
Bochkareva, N. I., E-mail: n.bochkareva@mail.ioffe.ru, Tarkhin, D. V., Rebane, Yu. T., Gorbunov, R. I., Lelikov, Yu. S., Martynov, I. A., & Shreter, Yu. G. Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures. United States. doi:10.1134/S1063782607010174.
Bochkareva, N. I., E-mail: n.bochkareva@mail.ioffe.ru, Tarkhin, D. V., Rebane, Yu. T., Gorbunov, R. I., Lelikov, Yu. S., Martynov, I. A., and Shreter, Yu. G. Mon . "Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures". United States. doi:10.1134/S1063782607010174.
@article{osti_21088455,
title = {Quantum efficiency and formation of the emission line in light-emitting diodes based on InGaN/GaN quantum well structures},
author = {Bochkareva, N. I., E-mail: n.bochkareva@mail.ioffe.ru and Tarkhin, D. V. and Rebane, Yu. T. and Gorbunov, R. I. and Lelikov, Yu. S. and Martynov, I. A. and Shreter, Yu. G.},
abstractNote = {The spectra of electroluminescence, photoluminescence, and photocurrent for the In{sub 0.2}Ga{sub 0.8}N/GaN quantum-well structures are studied to clarify the causes for the reduction in quantum efficiency with increasing forward current. It is established that the quantum efficiency decreases as the emitting photon energy approaches the mobility edge in the In{sub 0.2}Ga{sub 0.8}N layer. The mobility edge determined from the photocurrent spectra is E{sub me} = 2.89 eV. At the photon energies hv > 2.69 eV, the charge carriers can tunnel to nonradiative recombination centers with a certain probability, and therefore, the quantum efficiency decreases. The tunnel injection into deep localized states provides the maximum electroluminescence efficiency. This effect is responsible for the origin of the characteristic maximum in the quantum efficiency of the emitting diodes at current densities much lower than the operating densities. Occupation of the deep localized states in the density-of-states 'tails' in InGaN plays a crucial role in the formation of the emission line as well. It is shown that the increase in the quantum efficiency and the 'red' shift of the photoluminescence spectra with the voltage correlate with the changes in the photocurrent and occur due to suppression of the separation of photogenerated carriers in the field of the space charge region and to their thermalization to deep local states.},
doi = {10.1134/S1063782607010174},
journal = {Semiconductors},
number = 1,
volume = 41,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The roles of V-shaped pits on the improvement of quantum efficiency in InGaN/GaN multiple quantum well (MQW) light-emitting diodes are investigated by numerical simulation. The simulation results show that V-shaped pits cannot only screen dislocations, but also play an important role on promoting hole injection into the MQWs. It is revealed that the injection of holes into the MQW via the sidewalls of the V-shaped pits is easier than via the flat region, due to the lower polarization charge densities in the sidewall structure with lower In concentration and (10–11)-oriented semi-polar facets.
  • The dependences of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes on the temperature and excitation level are studied. The experiment is performed for two luminescence excitation modes. A comparison of the results obtained during photo- and electroluminescence shows an additional (to the loss associated with Auger recombination) low-temperature loss in the high-density current region. This causes inversion of the temperature dependence of the quantum efficiency at temperatures lower than 220–300 K. Analysis shows that the loss is associated with electron leakage from the light-emitting-diode active region. The experimental data are explained using the ballistic-overflow model. The simulationmore » results are in qualitative agreement with the experimental dependences of the quantum efficiency on temperature and current density.« less
  • We report on the band-edge stimulated emission in InGaN{endash}GaN multiple quantum well light-emitting diodes with varying widths and barrier thicknesses of the quantum wells. In these devices, we observe that the stimulated emission peak wavelength shifts to shorter values with decreasing well thickness. From the comparison of the results of the quantum mechanical calculations of the subbands energies with the measured data, we estimate the effective conduction- and valence-band discontinuities at the GaN{endash}In{sub 0.13}Ga{sub 0.87}N heterointerface to be approximately 130{endash}155 and 245{endash}220 meV, respectively. We also discuss the effect of stress on the estimated values of band discontinuities. {copyright} {italmore » 1997 American Institute of Physics.}« less
  • The temperature dependence of the radiative recombination zone in InGaN/GaN multiple quantum well light-emitting diodes is investigated. >From the electroluminescence spectra measured at various temperatures, it is found that there are two peaks at about 400 and 460 nm, which can be assigned as Mg-related and quantum well transitions, respectively. The behavior of these two peaks with temperature is modeled by the two rate equation. Based on this model, we deduce the activation energy of Mg in GaN films to be about 126 meV, which is consistent with reported results obtained by other techniques. {copyright} 2001 American Institute of Physics.
  • The spontaneous emission (SE) of InGaN/GaN quantum well (QW) structure with silver(Ag) coated on the n-GaN layer has been investigated by using six-by-six K-P method taking into account the electron-hole band structures, the photon density of states of surface plasmon polariton (SPP), and the evanescent fields of SPP. The SE into SPP mode can be remarkably enhanced due to the increase of electron-hole pairs near the Ag by modulating the InGaN/GaN QW structure or increasing the carrier injection. However, the ratio between the total SE rates into SPP mode and free space will approach to saturation or slightly decrease formore » the optimized structures with various distances between Ag film and QW layer at a high injection carrier density. Furthermore, the Ga-face QW structure has a higher SE rate than the N-face QW structure due to the overlap region of electron-hole pairs nearer to the Ag film.« less