Reliability Of Laser Diodes Research Articles

Extremely long lifetime of III-nitride laser diodes grown by plasma assisted molecular beam epitaxy

In this paper the reliability of III-nitride blue laser diodes grown by plasma-assisted molecular beam epitaxy on low threading dislocation density Ammono-GaN substrates is studied. It is found that defects formed in the heavily Mg-doped electron blocking layer (EBL) strongly affect the lifetime of the devices. These defects are identified as basal stacking fault domains which create threading dislocations. The effect of the EBL growth conditions on their generation and influence on lifetime of devices is presented. By optimization of the growth conditions of the EBL the lifetime of III-nitride laser diodes has been increased from 2000 up to 100,000 h.

Reliability of laser diodes for laser satellite communication in space radiation environment

The reliability of laser diodes is important for use in satellite optical communication systems, which is significantly influenced by space radiation effects. Degradation of laser diodes is induced by incident particles whose arrivals obey Poisson distribution, and the impact of each particle obeys normal distribution. Therefore, degradation process is regarded as a composite process, and its distribution is subsequently deduced. Reliability characteristics are evaluated based on simulated degradation data, and the error of evaluation is analyzed.

Negative-T InGaN laser diodes and their degradation

We studied the InGaN laser diode, emitting in the blue region of the spectrum and characterized by a negative characteristic temperature T0. The corresponding decrease in the threshold current with the increase in temperature for this device is caused by the increased distance between the electron-blocking layer and the quantum wells. Because of the non-monotonic temperature dependence of laser parameters, we can demonstrate a correlation of the degradation rate with nonradiative part of the total device current. This result indicates the potential importance of the recombination processes occurring outside of the active region for the reliability of InGaN laser diodes.

Markov process based reliability model for laser diodes in space radiation environment

The reliability of laser diodes is a prerequisite for use in satellite optical communication systems, which is significant influenced by both displacement damage effect and annealing effect. A reliability model was proposed to evaluate the reliability and lifetime for laser diodes in space radiation environment. Degradation process is separated into discrete states, and reliability model is subsequently established based on Markov process. The Markov process consists of a Poisson process and an exponential process, representing the displacement damage effect and annealing effect, respectively. Reliability characteristics of a given laser diode are simulated over 100,000h, and applicability of this reliability model is demonstrated by analyzing the variety trend of probability density of performance states.

Further Investigations into the Effects of Temperature on a 975 nm Tapered Laser Bar Using Convolution to Ascertain the Dominant Effect of Temperature on a Laser Bar

Temperature continues to be an issue in the reliability of high power laser diodes. Any effort, therefore, made to understand the dynamics of temperature on the performance of laser diodes is important. This is because it serves as a catalyst for the generation of nonradiative recombination centers, which ultimately kills laser diodes. In this paper, the convolution of simulation results was done to compare it with experimental results, which revealed more details that hitherto, could not have been captured by experiments alone. The inability of experiments to capture these details is due to the limited spatial resolution of the charged-coupled device (CCD) camera, which is approximately 30 µm much larger than the thickness of the quantum well active region used in the experiment. The convolution results showed a further smile-shaped profile within the four groups of array emitters, which in the experimental results, were considered as one emitter due to the limited spatial resolution of the CCD camera. The use of convolution to determine more details was investigated, due to the dominant effect of temperature found across the output power distribution of high power semiconductor laser diode bars.

Reliability evaluation for Blu-Ray laser diodes

With this paper we describe an extensive analysis of the reliability of InGaN-based laser diodes, emitting at 405 nm. These devices have excellent characteristics for application in the next-generation optical data storage systems. The analysis aims at describing the degradation process, as well as at investigating the role of current in determining the degradation rate. The results obtained within this paper suggest that the degradation of the laser diodes is correlated to the increase in the non-radiative recombination rate, with subsequent worsening of the optical properties of the devices. Furthermore, our findings support the hypothesis that current is the main driving force for degradation, while temperature and optical power play only a limited role in determining the degradation kinetics.

Efficient Outdiffusion of Hydrogen from Mg-Doped Nitrides by NF3 Annealing

High concentration (more than 1 × 1018 cm−3) of hydrogen atoms remaining in Mg-doped GaN epitaxial layers grown by metalorganic chemical vapor deposition even after conventional annealing in N2 ambient could induce degradation in GaN-based devices containing Mg-doped layers. In this study, by annealing Mg-doped nitrides in NF3 ambient, we successfully reduced residual hydrogen below mid-1017 cm−3, which is much smaller than by N2 annealing. NF3 annealing enhances outdiffusion of hydrogen from the bulk, which is possibly because the nitrogen and fluorine radicals decomposed from NF3 accelerate desorption of hydrogen adatoms from the surface. The proposed method for Mg activation would improve the reliability of GaN-based light-emitting diodes and laser diodes.

Improving Reliability of cw Bar Laser Diodes by Novel Mounting

High power bar laser diodes, with CW optical power output were studied experimentally. A novel mounting was designed to bring the coolant as close as possible to the laser bar in order to improve the bar laser diode characteristics. Thermal properties can influence significantly device characteristics, affecting wavelength, maximum output power, threshold current, slope efficiency and operating lifetime. Stable emission (803 nm) of the bar laser diodes was maintained during the investigation since it is very important for different kinds of applications. A high external quantum efficiency of (1.66) and a characteristic temperature of (106 oC) were obtained in our experimental setup. A reliable and high performance IR bar laser diode source was achieved experimentally.

Laser diode burn-in and reliability testing

More than 99 percent of all lasers manufactured in the world today are semiconductor laser diodes. Reliability is a concern in every laser diode application, whether it is a simple $10 laser pointer or a space-qualified optical transmitter link. The commercial success of a laser supplier rests largely on his ability to develop a robust manufacturing process that consistently produces reliable devices combined with the quantitative assurances he can provide to his customers proving the reliability of his devices. Over the past two decades, laser diode reliability testing techniques and equipment have evolved to support the diverse development of laser diodes.

B241 DVDドライブ用光ピックアップの放熱検討(エレクトロニクス機器・デバイスのサーマルマネージメント3)

In recent years, the recording speed of optical disc drives is increasing. Along with this, the power consumption of laser diodes in optical pickups is increasing. Although, reliability of laser diodes depends on temperature, we need to design the laser diode to operate at appropriate temperature. Therefore, precise prediction of laser diode temperature by thermal analysis has become important. We measured the distribution of the heat transfer coefficient around an optical pickup for various rotating speeds of an optical disc, and applied this to thermal analysis. We confirmed that the temperature of a laser diode can be predicted with high accuracy using this method.

Noise measurements of InGaAsP/InP laser diodes near the threshold current

Investigation of noise characteristics of InGaAsP/InP multiple-quantum-well laser diodes (LDs) near the threshold current region with the aim to reveal the LD quality and reliability problems is presented. A low quality and rapid degradation of particular laser diodes are reflected in noise characteristics: correlation factor between the optical and electrical fluctuations just after the threshold has a deep minimum and even drop to the negative values. The latter values are caused by leakage currents through the defects which determine the low quality and reliability of laser diodes. Optical noise intensity of a semiconductor laser below the threshold (here they operate as light emitting diodes) is low and the own noise level of a photodetector and measurement circuit is equal or exceeds it. In this case the laser diode optical noise has been measured using the correlation function method that increases optical noise measurement sensitivity by about three orders of magnitude.

155 Mbit/s transmission using ASE-injected Fabry-Perot laser diode in WDM-PON over 70°C temperature range

Thermal reliability of an uncooled Fabry-Perot laser diode (F-PLD) wavelength-locked to spectrum-sliced amplified spontaneous emission (ASE) as a source for wavelength division multiplexed-passive optical networks (WDM-PONs) is presented. An F-PLD with narrow mode spacing and asymmetric facet reflectivity relieved temperature dependency of transmission and power requirement of ASE injection. The chip temperature range of error-free transmission at 155 Mbit/s extended over 70°C with −22 dBm ASE injection.

Laser diode reliability: crystal defects and degradation modes

Degradation analysis is a crucial issue for the improvement of high power laser diodes. Degradation occurs in three different modes: rapid, gradual and catastrophic. It can be located inside the cavity or at the facet mirrors. Each type of degradation presents its own signature and different crystal defects appear associated with them. The main physical mechanisms responsible for laser degradation are analysed showing the relation between the main degradation modes and the different materials properties of the laser structures. To cite this article: J. Jiménez, C. R. Physique 4 (2003).

Optical semiconductor device reliability

Based on the degradation modes and mechanisms clarified in 1980s and 1990s, reliability of laser diodes and photodiodes is discussed for application to current optical fiber networks such as communication systems employing wavelength-division-multiplexing technique (WDM), high-frequency modulation technique, etc.

Comparison of the Strain and Stress in Bonded and Epitaxial Gallium Arsenide on Silicon by Photoreflectance Spectroscopy Measurements

ABSTRACTThe presence of an internal strain arising from the GaAs/spin-on-glass (SOG)/Si bonding procedure was investigated. In addition, the magnitude of any residual stress at room temperature and the mechanisms that may impose a stress, leading to elastic or plastic deformation of the bonded GaAs films, were identified.A comparative study of biaxial strain and stress, as a function of temperature in the range of 80- 300 K, in a bonded 2 μm-thick GaAs/SOG/Si sample and in an epitaxial 2 μm-thick GaAs/Si sample, grown by molecular beam epitaxy (MBE), will be presented. The type and magnitude of strain were determined by photoreflectance spectroscopy. In the case of GaAs/SOG/Si, the strain in the GaAs layer was found to be negligible, with compressive character, at room temperature and tensile in all other measured temperatures, whereas for the epitaxial GaAs/Si, the strain was taking significant tensile values in all temperatures. Furthermore, the strain for both samples was increasing with temperature reduction, as it is expected for a thermal strain induced by the different thermal expansion coefficients of GaAs and Si.The comparative study indicated clearly that the bonded GaAs/SOG/Si films are essentially strain-free at room temperature. This is a very important result for the good reliability of laser diodes that can be processed from such bonded GaAs material, which also has a crystal quality similar to that of the available GaAs substrates.

Correlation between the reliability of laser diodes and the crystal perfection of epitaxial layers estimated by high-resolution x-ray diffractometry

The dependence of the degradation of high-power quantum-well GaAs/AlGaAs laser diodes, grown by molecular-beam epitaxy, on the crystal perfection of the individual layers of the heterostructure is investigated. The crystal perfection of the layers is estimated by highresolution x-ray spectrometry. A numerical fit of the diffraction-reflection curves is performed using the Debye-Waller static factor. It is shown that considerably higher crystal perfection of laser heterostructures can be obtained by using as the waveguide layers binary AlAs/GaAs superlattices instead of the solid solution AlGaAs.

Significant progress in II-VI blue-green laser diodelifetime

A II-VI laser diode lifetime of > 140 h at 40°C, as well as ~400 h at 20°C, has been achieved for a ZnCdSe/ZnSSe/ZnMgSSe separate-confinement heterostructure laser diode under continuous-wave operation with a constant output power of 1 mW. Progress has been made towards increasing the basic reliability of ZnMgSSe-based wide bandgap laser diodes by reducing point defects.

Reliability study on 50-100-mW CW operation of 680-nm visible laser diodes with a window-mirror structure

We have studied reliability of 680-nm visible laser diodes (LDs) with a window-mirror structure formed by zinc-diffusion-induced disordering of GaInP quantum wells. Aging tests under the condition of CW output power in the range of 50-100 mW for ambient temperature from 40/spl deg/C to 70/spl deg/C have been carried out for 650-/spl mu/m-long LDs and 900-/spl mu/m-long LDs with three kinds of the front facet reflectivities (1.5%, 6% and 13%). In all tests, laser operation was stable for over 5000 h. For example, reliable 500-10000-h operation of the 900-/spl mu/m LDs was realized under the conditions of output power of 50 mW at 70/spl deg/C, 70 mW at 60/spl deg/C, and 100 mW at 40/spl deg/C for the first time. By various aging test results, dependence of the temperature and the output power on increase of the operating current has been investigated. Also, influences of the facet reflectivities and the cavity lengths on the reliability have been studied with focus on the optical power density and the current density. Consequently, it has been clarified that the degradation of the window LDs rather strongly depends on the operating current density than the optical power density. Moreover, it has been proven that the reliability of the window LDs is effectively improved by the reduction of the operating current density due to extension of the cavity length.

Strain-overcompensated GaInP-AlGaInP quantum-well laser structures for improved reliability at high-output powers

Strain-overcompensated multiple-quantum-well (MQW) laser structures have been analyzed theoretically as well as experimentally for the first time. Strain overcompensation reduces the bandgap shrinkage that normally takes place at the facets of compressively strained layers because of strain relaxation. This results in a lower absorption of the laser spot leading to a remarkable improvement of the reliability of high-power laser diodes.

10000 h, 30–50 mW CW operation of 670–690nm visible laser diodes

The reliability of high-power AlGaInP red laser diodes with strained DQW (double quantum well) active layer and an MQB (multiquantum barrier) has been investigated. For the non-window 690 nm lasers and the 670 nm window lasers 10000 h CW operation under the conditions of 60°C, 30 mW and 30°C, 50 mW, respectively, was realised.