Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

Abstract

Articles you may be interested inStrain reduction and crystal improvement of an InGaN/GaN quantum-well light-emitting diode on patterned Si (110) substrate Appl.Three dimensional numerical study on the efficiency of a core-shell InGaN/GaN multiple quantum well nanowire light-emitting diodes Effect of an electron blocking layer on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes Appl.Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells. V C 2015 AIP Publishing LLC. [http://dx.

Monolithic Broadband InGaN Light-Emitting Diode

“…In terms of photon energies, the line width broadening from 2.5 kW/cm 2 to 46 kW/cm 2 is ∼10 meV, which is relatively small compared to the corresponding peak shift of ∼60 meV. Thus, the blue-shift is believed to be mainly due to the screening of the piezoelectric field over the band-filling effect that give rise to spectral broadening, 18,19 indicating incomplete relaxation of strain in the tips. According to the nf-PL intensity map of Figure 3a, the signals at the sidewalls of the disks and at the tips are generally stronger than those from the central regions of the disks; this is attributed to higher internal quantum efficiencies (IQE) at the strain-relaxed regions as a result of increased electron−hole wave function overlap.…”

“…In terms of photon energies, the linewidth broadening from 2.5 kW/cm 2 to 46 kW/cm 2 is ~10meV, which is relatively small compared to the corresponding peak shift of ~60meV. Thus the blue-shift is believed to be mainly due to the screening of the piezoelectric field over the band-filling effect that give rise to spectral broadening,[(18), (19)] indicating incomplete relaxation of strain in the tips.…”

Reduction of Polarization Field Strength in Fully Strained c-Plane InGaN/(In)GaN Multiple Quantum Wells Grown by MOCVD

“…Here, we neglected the effects of bandgap normalization and band-filling, since the photo-excited carrier density in this study is relatively low around 10 17  cm −3 . More detailed consideration of each effect can be found in Ref 15. The theoretical polarization strength is calculated according to the non-linear polarization reported by Fiorentini and Barnardini et al [3].…”

“…The Stokes-like shift energy in the 16% InGaN quantum wells was determined to be 0.08 eV experimentally [15]. When the indium content increases, the Stokes-like shift energy also increases due to larger indium composition fluctuation.…”

InGaN/GaN Quantum Dot Light-Emitting Diodes on Silicon with Coalesced GaN Nanowire Buffer Layer

“…The room-temperature peak is centered at 475 nm. The internal quantum efficiency (IQE) was estimated (a maximum value) to be 25%, taken as the ratio of the integrated PL intensity at 300 and 13 K. Here, we assume a negligible nonradiative recombination of photogenerated carriers at the lowest cryogenic temperature (13 K). , Strong oscillations are observed in the measured spectra due to reflections at the GaN/Si interface. , Weak GaN emission is visible at lower temperatures, as most of the radiative recombination takes place within the quantum dots. The small peak at ∼535 nm is from the exciting laser.…”