Oxygen-induced high diffusion rate of magnesium dopants in GaN/AlGaN based UV LED heterostructures

Michałowski, Paweł Piotr; Złotnik, Sebastian; Sitek, Jakub; Rosiński, K.; Rudziński, M.

doi:10.1039/c8cp01470a

Cited by 17 publications

(11 citation statements)

References 26 publications

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“…The overall profile of the growth surface (Figure f) is consistent with enhanced growth at the trench edge due to faster growth rates on semipolar or concave growth fronts . Consistent with (2), high Mg incorporation rates are expected for H-rich semipolar and polar surfaces in an MOCVD growth environment. , Finally, the Ga diffusion length is expected to be much greater than that of Mg under these growth conditions. , …”

Section: Resultssupporting

confidence: 67%

“…55,56 Finally, the Ga diffusion length is expected to be much greater than that of Mg under these growth conditions. 57,58 The high concentration of Mg at the trench sidewall and the associated Mg clustering (Supporting Information Figure S4a) are also consistent with this picture. The nominally a-plane vertical sidewall of the trench is invariant in position, suggesting a low Ga incorporation coefficient, and correspondingly, an abundance of Ga vacancy sites for substitutional Mg incorporation.…”

Section: ++supporting

confidence: 70%

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Selective Area Regrowth Produces Nonuniform Mg Doping Profiles in Nonplanar GaN p–n Junctions

Chang

Wang

et al. 2021

ACS Appl. Electron. Mater.

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Nonplanar GaN p–n junctions formed by selective area regrowth were analyzed using pulsed laser atom probe tomography. Dilute Al marker layers were used to map the evolution of the p-GaN growth interface, enabling extraction of time-varying growth rates for nonpolar, semipolar, and polar surfaces from the trench edge to the center, respectively. The Mg dopant concentration is facet-dependent and varies inversely with the growth rate for the semipolar facets that grow rapidly away from the trench sidewalls. The negligible growth on the vertical sidewall of the trench coincides with an order of magnitude higher Mg concentration and substantial clustering of likely inactive dopants. A high Mg concentration is also observed near the regrowth interface of polar and semipolar planes, which we attribute to etching damage. We conclude that device fabrication processes employing selective area regrowth on nonplanar interfaces should consider both the spatial and temporal dependencies of growth rate that lead to nonuniform doping and explore growth conditions that could reduce variations in growth rate when nonuniform doping would adversely affect device performance.

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Section: Resultssupporting

confidence: 67%

Section: ++supporting

confidence: 70%

Selective Area Regrowth Produces Nonuniform Mg Doping Profiles in Nonplanar GaN p–n Junctions

Chang

Wang

et al. 2021

ACS Appl. Electron. Mater.

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“…Figure 4 presents elemental depth profiles for the as-grown, P-implanted and annealed at 1000°C (Al)GaN:Mg; Mg and P profiles were normalized to the adequate references. Similarly to our previous studies on Mg diffusion in (Al)GaN compounds [6,38], the Mg concentration gradually increases towards the surface, reaching [ 10 19 cm -3 , independently on implantation and annealing conditions. Thus, it can be stated that during P implantation, the Mg ions do not diffuse across the structures.…”

Section: Elemental Depth Profilingsupporting

confidence: 81%

Phosphorus implantation of Mg-doped (Al)GaN heterostructures: structural examination and depth profiling

Piętak

Złotnik

Rozbiegała

et al. 2020

J Mater Sci: Mater Electron

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Phosphorus introduction into Mg-doped aluminium gallium nitride ((Al)GaN) epilayers to enhance the acceptor activation is a possible strategy for a p-type conductivity improvement in III-nitride wide-bandgap semiconductors. To date, P-implanted Mg-doped (Al)GaN structures have not been systematically evaluated, regarding structural verification and elemental distribution. Here, comprehensive studies of P ions impact on structural degradation are presented. Furthermore, a post-implantation annealing conducted at different temperatures is examined as well. The results demonstrated that the structural changes in the examined compounds, namely GaN and Al0.1Ga0.9N, due to P implantation and a subsequent recovery by thermal annealing follow similar trends. Interestingly, it was revealed that P diffusion length is higher in AlGaN than in GaN, possibly due to higher oxygen content in Al-containing compounds, analogous to Mg dopant. Additionally, the initial Mg concentration in (Al)GaN is crucial because too high Mg doping could be the main cause of electrical properties degradation of (Al)GaN heterostructures after P ion implantation.

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“…The most influential challenge is the low injection efficiency of holes towards the MQWs of the UV emitters, which further stymies the external quantum efficiency (EQE), as well as low light output power (LOP). These low hole injection problems have various possible causes such as the high activation energy of Mg atoms in AlGaN (∼200 meV in GaN and reaches up to ∼630 meV in AlGaN), the low solubility of Mg in AlGaN, compensation by nitrogen vacancies, the formation of Mg-H complexes and, last but not least, the existence of unwanted and uninvited impurities like hydrogen (H), oxygen (O), and carbon (C) accompanying the Mg-H complex in the p-AlGaN hole source layer (HSL) and p-AlGaN contact layer (CL) [19][20][21][22][23][24]. To overcome low hole injection and high operating voltages, Zhong et al have introduced Mg Ga -O N delta codoping in AlGaN to enhance p-doping [18].…”

Section: Introductionmentioning

confidence: 99%

Suppressing the efficiency droop in AlGaN-based UVB LEDs

et al. 2021

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The optoelectronic properties of semiconducting aluminum gallium nitride (AlGaN)-based ultraviolet-B (UVB) light-emitting diodes (LEDs) are crucial for real-world medical applications such as cancer therapy and immunotherapy. However, the performance of AlGaN-based UVB LED devices is still poor due to the low hole injection efficiency. Therefore, we have numerically investigated the performance of AlGaN-based UVB LEDs for the suppression of efficiency droop as well as for the enhancement of hole injection in the multiquantum wells (MQWs). The influence of the undoped (ud)-AlGaN final quantum barrier (FQB), as well as the Mg-doped multiquantum barrier electron blocking layer (p-MQB EBL), on the efficiency droop has been focused on specifically. To evaluate the performance of the proposed device, we have compared its internal quantum efficiency (IQE), carrier concentration, energy band diagram, and radiative recombination rate with the conventional device structure. Furthermore, the influence of Al composition in the Al-graded p-AlGaN hole source layer (HSL) on the operating voltages of the proposed UVB LEDs was considered. The simulation results suggest that our proposed structure has a high peak efficiency and much lower efficiency droop as compared to the reference structure (conventional). Ultimately, the radiative recombination rate in the MQWs of the proposed UVB LED-N structure has increased up to ∼73%, which is attributed to the enhanced level of electron and hole concentrations by ∼64% and 13%, respectively, in the active region. Finally, a high efficiency droop of up to ∼42% in RLED has been successfully suppressed, to ∼7%, by using the optimized ud-AlGaN FQB and the p-MQB EBL, as well as introducing Al-graded p-AlGaN HSL in the proposed UVB LED-N structure.

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Oxygen-induced high diffusion rate of magnesium dopants in GaN/AlGaN based UV LED heterostructures

Cited by 17 publications

References 26 publications

Selective Area Regrowth Produces Nonuniform Mg Doping Profiles in Nonplanar GaN p–n Junctions

Selective Area Regrowth Produces Nonuniform Mg Doping Profiles in Nonplanar GaN p–n Junctions

Phosphorus implantation of Mg-doped (Al)GaN heterostructures: structural examination and depth profiling

Suppressing the efficiency droop in AlGaN-based UVB LEDs

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