Control of the Mg doping profile in III-N light-emitting diodes and its effect on the electroluminescence efficiency

Köhler, K.; Stephan, T.; Pérona, A.; Wiegert, J.; Maier, M.; Kunzer, M.; Wagner, J.

doi:10.1063/1.1901836

Cited by 69 publications

(34 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The exposure to high temperature can also induce modifications in the Mg profile, due to the diffusion of the acceptor atoms within the device structure. 4,5 For a careful optimization of the growth and processing conditions of GaN-based LEDs, it is important to understand how high temperatures can modify the internal structure of the devices, and in particular the distribution of structural defects such as dislocations, and the profile of the acceptor doping. Although relevant results have been described by the studies quoted above, no extensive analysis of the impact of high temperatures on the crystalline quality and on the Mg profile has been presented up to now.…”

mentioning

confidence: 99%

Impact of thermal treatment on the optical performance of InGaN/GaN light emitting diodes

et al. 2015

View full text Add to dashboard Cite

This paper describes a detailed analysis of the effects of high temperatures on the optical performance and structural characteristics of GaN-based LED structures with a high threading dislocation density. Results show that, as a consequence of storage at 900 °C in N2 atmosphere, the samples exhibit: (i) an increase in the efficiency of GaN and quantum-well luminescence, well correlated to an increase in carrier lifetime; (ii) a decrease in the parasitic luminescence peaks related to Mg acceptors, which is correlated to the reduction in the concentration of Mg in the p-type region, detected by Secondary Ion Mass Spectroscopy (SIMS); (iii) a diffusion of acceptor (Mg) atoms to the quantum well region; (iv) a reduction in the yield of Rutherford Backscattering Spectrometry (RBS)-channeling measurements, possibly due to a partial re-arrangement of the dislocations, which is supposed to be correlated to the increase in radiative efficiency (see (i))

show abstract

mentioning

confidence: 99%

Impact of thermal treatment on the optical performance of InGaN/GaN light emitting diodes

et al. 2015

View full text Add to dashboard Cite

show abstract

“…In addition to studying the piecewise homogeneous structures, we also compare them to structures where the GaN interlayer (thickness d i ) blocking Mg diffusion to the quantum well (QW) during growth [14] has been replaced by a 100 nm thick linearly graded In 7.5 Ga 92.5 N-GaN material layer where the n-type polarization doping [15] is fully neutralized by an equivalent p-type impurity doping. For simplicity, the AR consists of a single In 15 Ga 85 N QW in all the structures, the contact separation between the n-and p-type contacts is set to 1 µm and the total width of the n-contact fingers of the DHJ structures is 10% of the p-contact width d p .…”

mentioning

confidence: 99%

Elimination of Lateral Resistance and Current Crowding in Large‐Area LEDs by Composition Grading and Diffusion‐Driven Charge Transport

Kivisaari

Kim

Suihkonen

et al. 2017

Adv Elect Materials

View full text Add to dashboard Cite

from the resistance of the CSL, and they also reduce the effective area of the ohmic contacts and further aggravate the droop.To mitigate the effects of the resistive losses, Hurni et al. recently showed that increasing the thickness of the n-type CSL leads to significantly less pronounced current crowding and improves the wall-plug efficiency of LEDs at large currents. [8] However, this approach still necessitates using expensive bulk GaN substrates and a part of the active region (AR) needs to be cut out to deposit n-type contacts, exposing the edges of the AR to surface recombination. The basic structure of Hurni's low resistance LEDs as well as essentially all conventional LEDs relies on a double heterojunction (DHJ) design, where electrons and holes are injected to the AR from nand p-doped regions located on the opposite sides of the AR. This sets evident limitations to designing the structures so that the contacts do not substantially decrease the total AR area or increase the free surface area susceptible to surface recombination. To avoid some of the limitations of conventional DHJ structures related to device scaling, resistive losses and electrical excitation in general, diffusion-driven charge transport (DDCT) was very recently introduced as an alternative way to electrically excite the AR of LEDs. [9][10][11][12] In DDCT, the pn junction is partly separated from the AR, and in contrast with conventional solutions it relies on transporting electrons and holes to the AR from the same side by bipolar diffusion, enabling additional degrees of freedom for designing new devices.For practical reasons, the previous works on DDCT have mainly focused on structures containing vertically formed pn-homojunctions, which entail potential barriers and lead to suboptimal device performance. In this paper, however, we show that the electrical inefficiencies observed earlier can be fully eliminated by adapting the DDCT concept to realize laterally doped heterojunction (LHJ) structures (see Figure 1), and that the SAG techniques needed to realize such LHJ devices do not compromise the internal quantum efficiency of the AR. Furthermore, our results show that the LHJ structures can be further engineered using appropriate material composition gradings, that can reduce the resistive heating of the devices even below the limit set by ideal conventional DHJ devices.The fundamental difference between the DHJ and LHJ structures is the placement and geometry of the doped p-and n-GaN charge injection regions, which are expected to mainly affect Gallium nitride based light-emitting diodes (LEDs) are presently fundamentally transforming the lighting industry, but limitations in the materials and fabrication methods of LEDs introduce substantial challenges to their future development. Among the remaining key bottlenecks of GaN LEDs are the resistive losses and current crowding that strongly increase the heat generation at high powers. In this work the authors show how a new design paradigm based on diffusion-driven charge transport (...

show abstract

“…The TEM-WBDF images obtained using different g-vectors (<0002> and <11-20>) did not, however, show the presence of these dislocations. It has been shown using secondary ion mass spectrometry that Mg can diffuse during the growth of Mgdoped capping layers into the underlying active quantum well regions of light emitting diodes (LEDs) and laser diodes [9,10]. The presence of Mg in the active region has also recently been linked to the reduction of the electroluminescence intensity of LEDs [9], which was suggested to result from the formation of deep non-radiative recombination centers, such as Mg-nitrogen vacancy complexes [11].…”

Section: Resultsmentioning

confidence: 98%

The effect of a Mg‐doped GaN cap layer on the optical properties of InGaN/AlGaN multiple quantum well structures

Graham

Dawson

Zhang

et al. 2006

Phys. Status Solidi (c)

View full text Add to dashboard Cite

We have studied the effect of depositing a Mg-doped GaN cap layer on near-ultraviolet emitting In 0.05 Ga 0.95 N/Al 0.05 Ga 0.95 N multiple quantum well structures, using photoluminescence spectroscopy and transmission electron microscopy. The room temperature (T = 300 K) photoluminescence spectra revealed a reduction in the integrated photoluminescence intensity of the capped structure, which is shown by time decay measurements to be due to greater competition from non-radiative recombination processes. The structural analysis of the samples using electron microscopy has not shown any evidence of Mg-induced defects. We suggest that the non-radiative recombination path is related to the diffusion of Mg atoms into the quantum well region and the formation of Mg-nitrogen vacancy complexes. 1 Introduction Nitride based quantum well structures emitting in the near-ultraviolet wavelength range are the subject of an increasing amount of interest, due to their potential for use in white light emitting diodes [1,2]. The production of light emitting diodes requires inclusion of the active multiple quantum well region within a p-n junction, the p-type layer normally consisting of an activated Mg-doped GaN layer.In this paper, we present a comparative study of the results of photoluminescence and transmission electron microscopy measurements on In 0.05 Ga 0.95 N/Al 0.05 Ga 0.95 N multiple quantum well structures grown with and without an additional Mg-doped GaN cap layer. We have found that the growth of such a p-type layer can be detrimental to the optical properties of quantum wells emitting with roomtemperature peak wavelengths of around 385 nm. Microstructural investigations have been used to try to identify the source of this deterioration of the optical properties.

show abstract

Control of the Mg doping profile in III-N light-emitting diodes and its effect on the electroluminescence efficiency

Cited by 69 publications

References 15 publications

Impact of thermal treatment on the optical performance of InGaN/GaN light emitting diodes

Impact of thermal treatment on the optical performance of InGaN/GaN light emitting diodes

Elimination of Lateral Resistance and Current Crowding in Large‐Area LEDs by Composition Grading and Diffusion‐Driven Charge Transport

The effect of a Mg‐doped GaN cap layer on the optical properties of InGaN/AlGaN multiple quantum well structures

Contact Info

Product

Resources

About