A detail study of both the optical and electrical low- frequency noise spectra and their correlation factor of graded-index separate-confinement-heterostructure, multiple quantum well strained-layer Fabri-Perot and distributed- feedback InGaAsP/InP laser diodes has been carried out under the wide current and temperature ranges. A particular attention was concentrated to the investigation of optical and electrical fluctuations due to the mode hopping effect, which was observed at specific forward currents and temperatures. Both electrical and optical noises at mode hopping areas have the Lorentzian type spectrum, and are very strongly correlated and very sensitive to temperature and facet reflectivity.
In the past twenty years there has been considerably effort spent in attempting to explain the temperature dependence of the threshold current (Ith) of InGaAsP-InP based semiconductor lasers. These efforts and the mechanisms which have been presumed responsible for this temperature dependence are reviewed. An alternate means of analyzing the threshold current temperature dependence of these lasers, based on a parameter Tmax (rather than the conventional To) is proposed, and a relationship between the parameter Tmax and adjustable device structural and material parameters is presented. Numerous experimental results are analyzed to evaluate the effects of: internal absorption loss; Auger recombination; carrier leakage; and, optical gain on the temperature dependence of InGaAsP-based lasers. It is concluded that the dominant effect on the threshold current temperature sensitivity stems from the temperature dependence of the optical and differential modal gain.
KEYWORDS: High power lasers, Semiconducting wafers, Laser damage threshold, Reliability, Monte Carlo methods, Temperature metrology, Telecommunications, Optical communications, Chlorine, Statistical analysis
Controlled lifetests totaling 1.9 million device hours have been carried out on a distributed feedback (DFB) laser emitting at a wavelength near 1.55 micrometers with an output power in excess of 50 mW. The degradation rate is typically found to decrease with increasing operating time for a wide range of drive currents and temperatures. The effective activation energy was found to be 0.52 eV. End of life was defined by the following three criteria: the maximum operating power decreasing to 48 mW; the change in the center wavelength due to aging equaling +/- 0.5 nm; the operating current increasing by 20% (approximately equals 40 mA). Conservative predictions of operating lifetime are made using the worst case of constant degradation over the lifetime and an activation energy of 0.4 eV. Less than 0.01% of the sample are expected to wear-out in 20 years at 30 degree(s)C. No random failures were observed giving a random failure rate below 32 FITs. These results provide a high degree of confidence that the 1550 nm MQW DFB high power laser structure investigated is fit for both high speed optical communications and CATV systems.
We have measured the time-resolved photoconductive response of a strained InGaAs/InGaAsP/InP multiple quantum well laser structure as a function of temperature and bias. It is found that the hole escape is dominated by tunneling at reverse biases of greater than -0.5 V at all temperatures. Under forward bias, recombination is dominant at temperatures below approximately 90 K while thermal escape processes prevail at higher temperatures. From Arrhenius plots of the hole escape time, the activation energy from the ground level has been determined as a function of bias and is in good agreement with a valence band offset of 75% of the total band offset. The intercepts of the plots yielded a scattering parameter of 6 ps. The carrier dynamics within the well were simulated using a simple model of thermionic emission and gave good qualitative agreement. The calculations indicate that the structures have the potential for extremely fast detection.
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