Degradation behavior and thermal properties of red (650 nm) high-power diode single emitters and laser bars - art. no. 645606 (original) (raw)

Degradation mechanisms beyond device self-heating in deep ultraviolet light emitting diodes

2009 IEEE International Reliability Physics Symposium, 2009

Lifetime measurements on single, packaged UV LEDs were performed under constant current injection at 20 and 75 mA (60 and 226 A/cm 2). The junction temperature at operation was found by micro-Raman spectroscopy to be 57 and 184 • C, respectively. Unbiased LEDs of similar characteristics placed in an oven baked at the equivalent operating junction temperatures showed a degradation in output power similar to that in the current injection devices during the initial 24 hours, but did not continue to degrade beyond that time. These studies imply that device heating, is correlated with the initial drop in output power during burn-in, but is not directly linked to the total degradation over the lifetime of the device. Time-resolved PL studies on the device active region as well as further electro-optic measurements indicate that the degradation is not due primarily to that of the active region, but may be associated with generation of point defects such as N-vacancies near the p-n junction.

Degradation model analysis of laser diodes

Journal of Materials Science: Materials in Electronics, 2008

Broad area laser diodes were subjected to accelerated aging until most devices failed. Cathodoluminescence images indicate dark spots after gradual degradation and dark lines after sudden failure. The aging curves were analyzed based on recombination enhanced defect generation and the Eyring model. The data were statistically evaluated by log-normal distribution of failure time and by nonlinear mixed-effects of degradation parameters. The reliability is estimated for long term device operation.

Screening of high power laser diode bars in terms of stresses and thermal profiles

2008

Within the project TRUST a total of about 600 actively cooled high power laser diode bars is analyzed. These devices are packaged by various project partners and by applying different packaging technologies. A number of analytical tools is applied to the devices, among others strain profiling by photocurrent spectroscopy. We present selected results such as the evolution of packaging-induced strains when advancing the technology from indium- to AuSn-soldering. The thermal properties of all devices are screened before the aging experiments by using thermal imaging. This involves monitoring of complete thermal profiles along each bar as well as the identification of "hot" emitters. These statistics turns out to be batch-specific and sensitive to the soldering technology used.

Comparison of facet temperature and degradation of unpumped and passivated facets of Al-free 940-nm lasers using photoluminescence

IEEE Journal of Quantum Electronics, 2005

Influences of facet degradation of Al-free In-GaAsP-GaAs 940-nm laser diodes were studied at power densities well below catastrophic optical mirror damage level using photoluminescence (PL) during normal operation and after a rigorous burn-in procedure. The shift in the PL peak of the cladding layer of the device is used to calculate the temperature of the facet. Devices with different facet treatments: untreated electron beam evaporation, untreated ion beam deposition, unpumped and passivated facets were compared. The results indicate that the degradation of facet is more severe for untreated and unpumped facets as compared to passivated facets. The results were also compared with power measurements, which show that the drop in the power during the first 50 h of operation is nonexistent for passivated facet devices leading to the conclusion that photo-induced oxidation is the major cause of the degradation of the facet and thus oxide removal and surface passivation are crucial to make stable laser diodes.

Thermal stability analysis of High Brightness LED during high temperature and electrical aging

Proceedings of SPIE - The International Society for Optical Engineering, 2007

In this paper we report the analysis of thermal stability of High Brightness Light Emitting Diode subjected to thermal and bias ageing. The degradation mechanisms of several families of commercial available devices were investigated. In the first part of the work we estimated thermal resistance and thermal behaviour under dc bias condition. After this thermal characterisation two different ageing tests were carried out on devices: thermal aging at high temperature levels without biasing the devices and accelerated dc stress at nominal current value (400mA). At each step a complete electrical and optical characterisation of aged devices was performed, in order to find a correlation between different aging and a better understanding of degradation mechanism. This characterisation included I-V measurements, optical power vs current characteristics and spectral analysis. During thermal stress we observed the increase of forward voltage at nominal current and the degradation of optical power with nearly exponential kinetics. We found that lifetimes were well correlated with stress temperature: therefore it was possible to find an activation energy of degradation mechanism of about 1.5eV. Moreover, modifications of spectral properties during electrical and thermal stress were found. Thus, a package level analysis was carried out in order to clarify the role of modification in optical properties of reflector cup and the efficiency of phosphors. Finally, evaluation of differential structure functions indicated that stress induces also the worsening of the properties of the chip-to-package thermal path: this phenomenon has been attributed to the partial detachment and degradation of the ohmic contacts.

By-emitter Emulation Enhancement Tool Using a Global Thermal Solver for the Degradation Emulation of a Calibrated 975 nm Tapered Laser Bar

American Journal of Electrical and Electronic Engineering, 2013

In this paper, Barlase has been taken a step further by emulating the degradation processes in high power semiconductor laser bars using an upgraded version of Barlase by the introduction of a global thermal solver to further deepen the understanding of the behaviour of laser bars. In this paper, the emulation of a real laser bar was investigated to emulate experimental results by simulating the experimental results in the view of finding a correlation between them. The results established show a more elaborate frown shaped power/current profile and a corresponding frown shaped temperature profile especially at the front facet of the laser bar. Even though a more elaborate frown shaped profile was realised in the power, current and temperature profiles, it fell short from what was seen in the experimental results. As the emulation of laser bar degradation has not been attempted before, further work is needed to achieve better agreement in the output power, current and temperature profiles to better the model.

Study of the degradation of AlGaAs-based high-power laser bars: V defects

Journal of Materials Science: Materials in Electronics, 2007

In this work we report the results of damage induced by aging tests of high power AlGaAs based laser bars. Post-laser aging the mirror and cavity degradations are studied by cathodoluminescence (CL). Following the analysis of the CL images the origin of the defects arising in the mirror surface and causing ulterior laser cavity degradation is discussed in terms of stress packaging and thermal stress induced processes. The latter is estimated by a finite element modelling of the thermomechanical properties of the laser heterostructure at the facet.

Microscopic defect induced slow-mode degradation in II–VI based blue–green laser diodes

Journal of Crystal Growth, 2000

We have studied the microdefect induced degradation mode in long-lifetime blue}green laser diodes (LDs) and light emitting diodes (LEDs) based on II}VI wide bandgap semiconductors. Microscopic deep defect centers in the LDs and LEDs are detected using mainly DLTS technique, coupled with ICTS methods. It is evidenced that a slow-mode degradation, commonly observed in dislocation-free LD devices, is caused by the generation and enhancement of microscopic deep centers during the device aging process. One possible degradation mechanism with a`carrier removal e!ecta is presented.

Measurement and Analysis of Thermal Parameters and Efficiency of Laser Heterostructures and Light-Emitting Diodes

Metrology and Measurement Systems, 2010

Measurement and Analysis of Thermal Parameters and Efficiency of Laser Heterostructures and Light-Emitting DiodesA thermal resistance characterization of semiconductor quantum-well heterolasers in the AlGaInAs-AlGaAs system (λst≈ 0.8 μm), GaSb-based laser diodes (λst≈ 2 μm), and power GaN light-emitting diodes (visible spectral region) was performed. The characterization consists in investigations of transient electrical processes in the diode sources under heating by direct current. The time dependence of the heating temperature of the active region of a source ΔT(t), calculated from direct bias change, is analyzed using a thermalRTCTequivalent circuit (the Foster and Cauer models), whereRTis the thermal resistance andCTis the heat capacity of the source elements and external heat sink. By the developed method, thermal resistances of internal elements of the heterolasers and light-emitting diodes are determined. The dominant contribution of a die attach layer to the internal therma...