Modeling the electrical characteristic of InGaN/GaN blue-violet LED structure under electrical stress

Roccato, Nicola; Piva, Francesco; Santi, Carlo De; Buffolo, Matteo; Haller, Camille; Carlin, J.-F.; Vallone, Marco; Tibaldi, Alberto; Bertazzi, Francesco; Goano, Michele; Verzellesi, Giovanni; Meneghesso, Gaudenzio; Zanoni, Enrico; Meneghini, Matteo

doi:10.1016/j.microrel.2022.114724

Cited by 6 publications

(4 citation statements)

References 40 publications

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“…Only after ageing, at voltages lower than 1 V, we have a measurable contribution in the leakage current due to the presence of other parasitic conduction paths [24], The contribution of this process has been modelized for simplicity by reducing the shunt resistance of the LED, as done also in previous reports [42,43]. Therefore, these results emulate a stress-induced increase in defects density confirming the hypothesis of the rise in defect concentration in the depletion region during ageing [8,16,44].…”

Section: Modeling Of Forward Leakage Current Increasesupporting

confidence: 81%

“…In this case, current conduction is assisted by the presences of deep defects located within the space charge region, which can help carriers tunnel and recombine non-radiatively through the active region [15]. Figure 2 shows an increase in the forward leakage current after stress, which was therefore associated to an increase in trap concentration in the depletion region during the ageing test [16].…”

Section: Experimental Investigationmentioning

confidence: 99%

“…The second process observed during ageing is the increase in the leakage current. Considering that the origin of such process is related to the presence of deep levels within the depletion region, we started our analysis by implementing TAT through the NLMs model proposed by Mandurrino et al, and previously adopted to describe the sub turn-on conduction in visible LEDs [15,16,37]. Specifically, a NLM is used to compute the probability of tunneling from a desired starting position toward the traps positioned within a specific device region, according to the equations reported in [15,37].…”

Section: Modeling Of Forward Leakage Current Increasementioning

confidence: 99%

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Modeling of the Electrical Characteristics and Degradation Mechanisms of UV-C LEDs

Roccato,

Piva,

De Santi

et al. 2024

IEEE Photonics J.

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In this paper we investigate the reliability of AlGaNbased UV-C LEDs with an emission wavelength of 265 nm. By submitting the devices to constant current stress, two main electrical degradation processes are identified: a turn-on voltage shift and an increase in the forward leakage current. In particular, these processes were respectively attributed to: (i) a partial passivation of the Mg-doping concentration in the region adjacent to the contact, probably caused by a local hydrogen diffusion, and ii) a diffusion/generation process of defects in the interlayer, responsible for the increase in the trap-assisted tunneling. To validate these hypotheses, we employed TCAD simulations by varying only the Mg-doping concentration in the region adjacent to the p-contact and the defect density in the interlayer. Thus, we correctly reproduced the experimental variation in electrical characteristics, confirming the physical mechanisms identified.

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Section: Modeling Of Forward Leakage Current Increasesupporting

confidence: 81%

Section: Experimental Investigationmentioning

confidence: 99%

Section: Modeling Of Forward Leakage Current Increasementioning

confidence: 99%

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Modeling of the Electrical Characteristics and Degradation Mechanisms of UV-C LEDs

Roccato,

Piva,

De Santi

et al. 2024

IEEE Photonics J.

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“…It has already been demonstrated that most LED products with high local strain have poor photoelectric performance and decrease in a short time [ 49 ], and in addition, the reliability also mainly includes the lifetime [ 50 ]. Recently, many articles have mentioned that the most important factor in affecting reliability is the thermal management problem of the LED packaging structure [ 51 , 52 ]. Therefore, the reliability of LED products depends on the cooling channels with reasonable design and on the materials with high heat conduction performance.…”

Section: Discussionmentioning

confidence: 99%

Micro-Raman for Local Strain Evaluation of GaN LEDs and Si Chips Assembled on Cu Substrates

Brugnolotto,

Mezzalira,

Conti

et al. 2023

Micromachines

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Integrated circuits are created by interfacing different materials, semiconductors, and metals, which are appropriately deposited or grown on substrates and layers soldered together. Therefore, the characteristics of starting materials and process temperatures are of great importance, as they can induce residual strains in the final assembly. Identifying and quantifying strain becomes strategically important in optimizing processes to enhance the performance, duration, and reliability of final devices. This work analyzes the thermomechanical local strain of semiconductor materials used to realize LED modules for lighting applications. Gallium Nitride active layers grown on sapphire substrates and Si chips are assembled by soldering with eutectic AuSn on copper substrates and investigated by Raman spectroscopy in a temperature range of −50 to 180 °C. From the Raman mapping of many different samples, it is concluded that one of the leading causes of strain in the GaN layer can be attributed to the differences in the thermal expansion coefficient among the various materials and, above all, among the chip, interconnection material, and substrate. These differences are responsible for forces that slightly bend the chip, causing strain in the GaN layer, which is most compressed in the central region of the chip and slightly stretched in the outer areas.

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Modeling the electrical degradation of AlGaN-based UV-C LEDs by combined deep-level optical spectroscopy and TCAD simulations

Roccato

Piva

Santi

et al. 2023

Applied Physics Letters

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The long-term stability of ultraviolet (UV)-C light-emitting diodes (LEDs) is of major importance for many applications. To improve the understanding in this field, we analyzed the degradation of AlGaN-based UVC LEDs and modeled the variation of electrical characteristics by 2D simulations based on the results of deep-level optical spectroscopy (DLOS). The increase in the forward leakage current observed during ageing was ascribed an increase in trap-assisted tunneling. The analysis of the degradation kinetics suggests the role of a defect diffusion process, possibly involving impurities coming from the p-type layers.

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Modeling the electrical characteristic of InGaN/GaN blue-violet LED structure under electrical stress

Cited by 6 publications

References 40 publications

Modeling of the Electrical Characteristics and Degradation Mechanisms of UV-C LEDs

Modeling of the Electrical Characteristics and Degradation Mechanisms of UV-C LEDs

Micro-Raman for Local Strain Evaluation of GaN LEDs and Si Chips Assembled on Cu Substrates

Modeling the electrical degradation of AlGaN-based UV-C LEDs by combined deep-level optical spectroscopy and TCAD simulations

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