Abstract
We present a detailed analysis of the gradual degradation mechanisms of InGaAs Light-Emitting Diodes (LEDs) tuned for optical emission in the 1.45–1.65 μm range. Specifically, we propose a simple and effective methodology for estimating the relative changes in non-radiative lifetime, and a procedure for extracting the properties of defects responsible for Shockley-Read-Hall recombination. By means of a series of accelerated aging experiments, during which we evaluated the variations of the optical and electrical characteristics of three different families of LEDs, we were able to identify the root causes of device degradation. Specifically, the experimental results show that, both for longer stress time at moderate currents or for short-term stress under high injection levels, all the devices are affected: (i) by a partial recovery of the optical emission at the nominal bias current; and (ii) by a decrease in the emission in low-bias regime. This second process was deeply investigated, and was found to be related to the decrease in the non-radiative Shockley-Read-Hall (SRH) lifetime due to the generation/propagation of defects within the active region of the LEDs. Devices tuned for longer-wavelength emission exhibited a second degradation process, which was found to modify the carrier injection dynamics and further speed-up optical degradation in the low bias regime. These processes were ascribed to the effects of a second non-radiative recombination center, whose formation within the active region of the device was induced by the aging procedure. Through mathematical analysis of the degradation data, we could quantify the percentage variation in SRH lifetime, and identify the activation energy of the related defects.
Highlights
Inx Ga1−x As alloys are of great interest for the optoelectronics industry, due to their widespread adoption for the manufacturing of short-wavelength infrared (SWIR) sensors, detectors, lasers, and photovoltaic cells [1,2,3,4]
In order to understand whether this stronger degradation should be ascribed to an acceleration of the defect generation process impacting on optical efficiency for shorter stress times, or if it should be ascribed to the propagation of a second kind of non-radiative recombination centers (NRRCs), we further investigated the role of trap level Et in the variation of the non-radiative lifetime
With this work we have extensively investigated the degradation mechanisms that can limit the reliability of InGaAs multi-quantum wells (MQWs) LightEmitting Diodes (LEDs) tuned for emission in the
Summary
Inx Ga1−x As alloys are of great interest for the optoelectronics industry, due to their widespread adoption for the manufacturing of short-wavelength infrared (SWIR) sensors, detectors, lasers, and photovoltaic cells [1,2,3,4]. The growth of other Inx Ga1−x As alloys, if not limited to layer thicknesses below the critical value, induces the formation of dislocations and other extended crystalline defects that may be detrimental for the reliable and efficient operation of devices based on this material The analysis of such defects, as well as the development of mitigation strategies for the epitaxial growth of devices through a metamorphic approach [5,6,7,8], were a focal point of the scientific and industrial research in the 1980s and in the 1990s. Results on this may be relevant for the development of advanced sources for silicon photonics based on III-As semiconductors, whose reliability is still under extensive study [12,13,14,15]
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