Internal quantum efficiency and carrier injection efficiency of <i>c</i>‐plane,  and  InGaN/GaN‐based light‐emitting diodes

Wang, Junjun; Meisch, Tobias; Heinz, Dominik; Zeller, Raphael; Scholz, F.

doi:10.1002/pssb.201552187

Cited by 11 publications

(10 citation statements)

References 12 publications

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“…Since our LEDs neither had an electron blocking layer nor an In-GaN underlayer below the QWs, the reduction of η inj at shorter wavelengths is probably caused by QWs which become too shallow for efficient injection and carriers start to overflow. A similar reduction of η inj has been reported when the internal fields are reduced in semi-polar QWs [34]. As mentioned before, the reduction of η inj towards longer wavelengths is likely caused by η e due to self-adsorption in the p-GaN, i.e.…”

Section: B Resultssupporting

confidence: 81%

Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

et al. 2017

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We measured the electro-luminescence of light emitting diodes (LEDs) on substrates with low dislocation densities (LDD) at 10 6 cm −2 and low 10 8 cm −2 , and compared them to LEDs on substrates with high dislocation densities (HDD) closer to 10 10 cm −2. The external quantum efficiencies (EQEs) were fitted using the ABC-model with and without localisation. The non-radiative recombination (NR) coefficient A was constant for HDD LEDs, indicating that the NR was dominated by dislocations at all wavelengths. However, A strongly increased for LDD LEDs by a factor of twenty when increasing the emission wavelength from 440 nm to 540 nm. We attribute this to an increased density of point defects due to the lower growth temperatures used for longer wavelengths. The radiative recombination coefficient B followed the squared wave function overlap for all samples. Using the observed coefficients, we calculated the peak efficiency as a function of the wavelength. For HDD LEDs the change of wave function overlap (i.e. B) is sufficient to reduce the EQE as observed, while for LDD LEDs also the NR coefficient A must increase to explain the observed EQEs. Thus reducing NR is important to improve the EQEs of green LEDs, but this cannot be achieved solely by reducing the dislocation density: point defects must also be addressed.

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Section: B Resultssupporting

confidence: 81%

Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

et al. 2017

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“…As mentioned above, the poor p-doping efficiency and the contact-barrier heights in GaN-based lightemitters highly hampers the carrier injection, reducing the overall EQE [41][42][43]. Therefore, to have a deeper understanding on the better current injection of the KOH-treated samples and to shed light on the electrical device performance, we studied the injection efficiency by employing the ABC model as follow [44]. We selected two devices (40 s KOH and as-grown) that showed an average current injection and EQE.…”

Section: Resultsmentioning

confidence: 99%

Enhanced electro-optic performance of surface-treated nanowires: origin and mechanism of nanoscale current injection for reliable ultraviolet light-emitting diodes

Priante

Tangi

Min

et al. 2018

Opt. Mater. Express

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Self-assembled nanowires are posed to be viable alternatives to conventional planar structures, including the nitride epitaxy for optoelectronic, electronic and nano-energy applications. In many cases, current injection and extraction at the nanoscopic scale are essential for marked improvement at the macroscopic scale. In this investigation, we study the mechanism of nanoscale current injection and the origin of improvement of the flow of charged carriers at the group-III nitride semiconductor surface and metal-semiconductor interfaces. Conductive atomic force microscopy (c-AFM) and Kelvin probe force microscopy (KPFM) enable a rapid analysis of the electrical and morphological properties of single and ensemble nanostructures. The surface potential and current injection of AlGaN nanowirebased LEDs are spatially mapped before and after surface treatment with KOH solution. Treated-nanowires showed an improved current spreading and increased current injection by nearly 10×, reduced sub-turn-on voltage (as low as 5 V), and smaller series resistance. The reduced contact potential confirms the lower semiconductor/metal barrier, thus enabling larger carriers flow, and correlates with the 15% increase in injection efficiency in macroscopic LEDs. The improvement leads to the normalization of nanoscale electrical conducting properties of UV AlGaN-based nanowire-LEDs and lays the foundation for the realization of practical nanowire-based device applications.

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“…Indeed, systematically higher in-jection losses in semipolar LEDs have been observed in a recent study. 59 If this loss of carriers is reduced by the internal fields, then screening of these fields at high currents on (0001) would open the same loss channel, which is already active in semi-polar LEDs and even stronger in non-polar LEDs. As a consequence, non-polar devices do not show much droop (as reported) but would always have a lower EQE, because their loss channel is already fully active at low current densities.…”

Section: Led Performancementioning

confidence: 99%

Comparative study of (0001) and InGaN based light emitting diodes

Pristovsek

Humphreys

Bauer

et al. 2016

Jpn. J. Appl. Phys.

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We have systematically investigated the doping of (1122) with Si and Mg by metal-organic vapour phase epitaxy for light emitting diodes (LEDs). By Si doping of GaN we reached electron concentrations close to 10 20 cm −3 , but the topography degrades above mid 10 19 cm −3. By Mg doping we reached hole concentrations close to 5×10 17 cm −3 , using Mg partial pressures about 3× higher than those for (0001). Exceeding the maximum Mg partial pressure led to a quick degradation of the sample. Low resistivities as well as high hole concentrations required a growth temperature of 900 • C or higher. At optimised conditions the electrical properties as well as the photoluminescence of (1122) p-GaN were similar to (0001) p-GaN. The best ohmic p-contacts were achieved by NiAg metallisation. A single quantum well LED emitting at 465 nm was realised on (0001) and (1122). Droop (sub-linear increase of the light output power) occurred at much higher current densities on (1122). However, the light output of the (0001) LED was higher than that of (1122) until deep in the droop regime. Our LEDs as well as those in the literature indicate a reduction in efficiency from (0001) over semi-polar to non-polar orientations. We propose that reduced fields open a loss channel for carriers.

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Internal quantum efficiency and carrier injection efficiency of c‐plane, and InGaN/GaN‐based light‐emitting diodes

Cited by 11 publications

References 12 publications

Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

Enhanced electro-optic performance of surface-treated nanowires: origin and mechanism of nanoscale current injection for reliable ultraviolet light-emitting diodes

Comparative study of (0001) and InGaN based light emitting diodes

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