Understanding peculiarities in the optoelectronic characteristics of light emitting diodes based on (In,Ga)N/GaN nanowires

Musolino, Mattia; Tahraoui, A.; Limbach, F.; Lähnemann, Jonas; Jahn, U.; Brandt, O.; Geelhaar, Lutz; Riechert, H.

doi:10.1063/1.4894241

Cited by 17 publications

(31 citation statements)

References 23 publications

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“…The EL spectra are characterized by a rather broad emission band consisting of two main transition lines, which exhibit a blue shift with increasing injected current, as marked by the magenta dashed arrows. Interestingly, similar asymmetric peaks with low energy tails have also been observed in other green NW-LEDs reported in literature with structures comparable to the one employed in this work [8,10,30,31]. However, only the integrated EL or the position of the most intense transition has been considered in all these cases.…”

Section: Introductionsupporting

confidence: 83%

“…In the last decade, III-N nanowires (NWs) have been often employed as basis for the fabrication of light-emitting diodes (LEDs) [1][2][3][4][5][6][7][8][9][10]. One of the main advantages of this approach is the elastic relaxation of the strain induced by lattice mismatch at the free sidewalls due to NW geometry [11,12], thus enabling along the NW axis the growth of high quality (In,Ga)N/GaN heterostructures with In content higher than in conventional planar LEDs.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Varying Three-Dimensional Strain on the Emission Properties of Light-Emitting Diodes Based on (In,Ga)N/GaN Nanowires

et al. 2017

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In the experimental electroluminescence (EL) spectra of light-emitting diodes (LEDs) based on N-polar (In,Ga)N/GaN nanowires (NWs), we observe a double-peak structure. The relative intensity of the two peaks evolves in a peculiar way with injected current. Spatially and spectrally resolved EL maps confirm the presence of two main transitions in the spectra and suggest that they are emitted by a majority of the single nano LEDs. In order to elucidate the physical origin of this effect, we perform theoretical calculations of the strain, electric field, and charge-density distributions for both planar LEDs and NW LEDs. On this basis, we simulate also the EL spectra of these devices, which exhibit a double-peak structure for N-polar heterostructures, in both the NW and the planar case. By contrast, this feature is not observed when Ga-polar planar LEDs are simulated. We find that the physical origin of the double-peak structure is a stronger quantum-confined Stark effect occurring in the first and last quantum well of the N-polar heterostructures. The peculiar evolution of the relative peak intensities with injected current, seen only in the case of the NW LED, is attributed to the three-dimensional strain variation resulting from elastic relaxation at the free sidewalls of the NWs. Therefore, this study provides important insights on the working principle of N-polar LEDs based on both planar and NW heterostructures

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Section: Introductionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Effect of Varying Three-Dimensional Strain on the Emission Properties of Light-Emitting Diodes Based on (In,Ga)N/GaN Nanowires

et al. 2017

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“…The colored spectra (normalized) represent the EL measured with the probe tip at four different positions on the unprocessed NW ensemble for a driving current of 100 nA. The black spectrum is the EL of the processed ensemble LED [12]. …”

Section: Resultsmentioning

confidence: 99%

“…Finally, Ti/Au bonding pads and an Al/Au n-type contact were deposited on the top contacts and on the back side of the Si substrate, respectively. A more detailed description of the growth and processing procedure as well as the EL and I – V characteristics of the NW-ensemble LED can be found in [12].…”

Section: Methodsmentioning

confidence: 99%

Electroluminescence and current–voltage measurements of single-(In,Ga)N/GaN-nanowire light-emitting diodes in a nanowire ensemble

Treeck¹,

Ledig²,

Scholz³

et al. 2019

Beilstein J. Nanotechnol.

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We present the combined analysis of electroluminescence (EL) and current–voltage (I–V) behavior of single, freestanding (In,Ga)N/GaN nanowire (NW) light-emitting diodes (LEDs) in an unprocessed, self-assembled ensemble grown by molecular beam epitaxy. The data were acquired in a scanning electron microscope equipped with a micromanipulator and a luminescence detection system. Single NW spectra consist of emission lines originating from different quantum wells, and the width of the spectra increases with decreasing peak emission energy. The corresponding I–V characteristics are described well by a modified Shockley equation. The key advantage of this measurement approach is the possibility to correlate the EL intensity of a single-NW LED with the actual current density in this NW. This way, the external quantum efficiency (EQE) can be investigated as a function of the current in a single-NW LED. The comparison of the EQE characteristic of single NWs and the ensemble device allows for a quite accurate determination of the actual number of emitting NWs in the working ensemble LED and the respective current densities in its individual NWs. This information is decisive for a meaningful and comprehensive characterization of a NW ensemble device, rendering the measurement approach employed here a very powerful analysis tool.

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“…More details about the employed LED structure, the growth parameters as well as the fabrication process can be found in our previous publications. 11,23…”

Section: Introductionmentioning

confidence: 99%

A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires

Musolino

Treeck

Tahraoui

et al. 2016

Journal of Applied Physics

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We investigated the origin of the high reverse leakage current in light emitting diodes (LEDs) based on (In,Ga)N/GaN nanowire (NW) ensembles grown by molecular beam epitaxy on Si substrates. To this end, capacitance deep level transient spectroscopy (DLTS) and temperature-dependent current-voltage (I-V) measurements were performed on a fully processed NW-LED. The DLTS measurements reveal the presence of two distinct electron traps with high concentrations in the depletion region of the p-i-n junction. These band gap states are located at energies of 570 ± 20 and 840 ± 30 meV below the conduction band minimum. The physical origin of these deep level states is discussed. The temperature-dependent I-V characteristics, acquired between 83 and 403 K, show that different conduction mechanisms cause the observed leakage current. On the basis of all these results, we developed a quantitative physical model for charge transport in the reverse bias regime. By taking into account the mutual interaction of variable range hopping and electron emission from Coulombic trap states, with the latter being described by phononassisted tunnelling and the Poole-Frenkel effect, we can model the experimental I-V curves in the entire range of temperatures with a consistent set of parameters. Our model should be applicable to planar GaN-based LEDs as well. Furthermore, possible approaches to decrease the leakage current in NW-LEDs are proposed. a) M. Musolino and D. van Treeck contributed equally to this work. b) Author to whom correspondence should be addressed. Electronic mail: treeck@pdi-berlin.de dependent current-voltage (I-V) measurements. On the basis of these data, we have developed a quantitative physical model able to describe the experimental I-V curves of NW-LEDs in the reverse bias regime for a wide range of temperatures. The assumptions made in this study should remain valid also for planar devices based on III-N heterostructures, thus making our model applicable also to conventional planar LEDs.The NW-LED structure employed in this work was grown by molecular beam epitaxy (MBE) on an AlN-buffered ndoped Si(111) substrate with the help of self-assembly processes. The active region of the NW-LED consists of four axial (In,Ga)N quantum wells (QWs) with an average In content of approximately 25%, separated by three GaN barriers. The last QW is immediately followed by a Mg-doped (Al,Ga)N electron blocking layer (EBL). The active region is embedded between two doped GaN segments designed such that an n-i-p diode doping profile is created. A schematic Si x O y n-Si(111) FIG. 1. (Color online) Schematic of the employed NW-LED structure. Note that the various dimensions are not to scale.

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Understanding peculiarities in the optoelectronic characteristics of light emitting diodes based on (In,Ga)N/GaN nanowires

Cited by 17 publications

References 23 publications

Effect of Varying Three-Dimensional Strain on the Emission Properties of Light-Emitting Diodes Based on (In,Ga)N/GaN Nanowires

Effect of Varying Three-Dimensional Strain on the Emission Properties of Light-Emitting Diodes Based on (In,Ga)N/GaN Nanowires

Electroluminescence and current–voltage measurements of single-(In,Ga)N/GaN-nanowire light-emitting diodes in a nanowire ensemble

A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires

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