Stark Effects Model Used to Highlight Selective Activation of Failure Mechanisms in MQW InGaN/GaN Light-Emitting Diodes

Abstract

This paper demonstrates the feasibility of creating specific defects in double-heterostructure InGaN/GaN commercial light-emitting diodes by neutron irradiation. Using controlled neutron energy, only one failure mechanism can be activated. Defects are located on the side of the chip and increase the leakage current driven by the well-known Poole-Frenkel effect with E c − E T = 130 meV electron trap energy level. The maximal amplitude of the optical spectrum also reveals a drop of about 20% associated with the rise of the leakage current. The Stark effect model highlights the origin of the degradation. Index Terms-GaN, physics of failure, quantum well, Stark effect. I. CONTEXT AND OBJECTIVESN UMEROUS papers have reported thermal and/or current activation drives to observe more than two different failure mechanisms in optoelectronic devices [1]. In this case, the extrapolation of degradation laws is exclusively empirical. For laser diodes, LEDs, and new technologies, this methodology is not perfectly suitable to extrapolate a lifetime distribution.One of the possible solutions in actual technologies consists of distinguishing each failure mechanism. However, the main difficulty is activating specific defects in the structure to isolate associated failure mechanisms. Generally, the volume of a single defect is close to 50 Å, which is weaker than the De Broglie wavelength of the material (240 Å for GaAs). In this case, the impact on optical transitions and transport of carriers in the structure must be analyzed using quantum theory [2]. To create such controlled defects in the structure, it is necessary to avoid classical accelerated tests and to propose new strategy. One solution consists of using particles that have an equivalent wavelength that is close to the defect area with energy higher than the covalent energy. In this context, we are going to demonstrate that controlled neutron energy irradiation is a useful methodology for selective activation of failure mechanisms in packaged double-heterostructure LEDs. Fig. 1. Internal structure of the MQW InGaN/GaN LED.Mixing nanodegradation and quantum theory in relation with carrier transport and optical transitions, quantum degradation laws are investigated. If the material dimension is larger than 100 nm, the degradation laws must be written using a continuous function. For nanocomponents, the degradation laws must be quantified. In the two cases, the quantum theory is well adapted, and the accurate model of degradation can be built for all technology.This paper highlights the feasibility of the methodology to activate only one kind of defects and adjust this methodology. Double-heterostructure LEDs (DH-LEDs) have been used because all failure mechanisms are well known: defect diffusion in the active zone, leakage current on the side of the chip, and gradual variations of series resistance [3]-[5]. In our case, the leakage current arises from specific neutron energy of about 2.9 MeV and weak flux (1850 cm −2 · s −1 ).The key issue is knowing if neutron irradiation c...

Optical performances degradation of InGaN/GaN MQW LEDs related to fluorescence shift of copolymer-based silicone coating

“…All of those models have been extensively studied by Deshayes et al and enable to build the complete theoretical L(E) model through equation 5 [26].…”