Robert A. Hawthorne

Reliability of various size oxide aperture VCSELs

This paper presents Honeywells most recent work on 850 nm oxide aperture vertical cavity surface emitting laser (VCSEL) reliability. The VCSELs studied have a range of aperture diameters from about 5 to 20 /spl mu/m and the reliability effect of aperture diameter is of principal interest in this paper. Larger apertures generally exhibit greater reliability. Electrostatic discharge (ESD) sensitivity thresholds of the various oxide aperture VCSELs is discussed, again showing dependence on diameter, with larger being better. Results for humidity exposure are presented. Here we find no aperture size dependence, because none of the tested designs show significant susceptibility to humidity-induced degradation. It is demonstrated that, in addition to end-of-life degradation, VCSELs generally exhibit variation of performance characteristics during the early part of operating life. This often leads to a requirement for device burn-in. Honeywells work in the area of wafer stabilization (trademarked under the name STABILAZE, patent pending) is introduced, showing how critical device parameters such as threshold and slope efficiency can be made to be unvarying over the products life without the need for costly component or module-level burn-ins.

Commercialization of Honeywell's VCSEL technology

In 1996, Honeywell was the first company to commercialize VCSEL technology, and today it is the worlds largest VCSEL component supplier. This paper will focus on the aspects of VCSEL manufacture that are important to maintain highly reliable and producible components. For current VCSEL products, we will address the evolution of VCSEL reliability and its effect on performance in data communications systems. New applications in both the data communications and sensor markets are being enabled by the VCSEL technology. This paper will also discuss new VCSEL structures, packages and wavelengths that are being commercialized by Honeywell to address these emerging markets.

Commercialization of Honeywell's VCSEL technology: further developments

Each year, more VCSEL technologies make the transition from research curiosities to commercially available products. In this paper we describe several such technologies at Honeywell, each at a different stage of that transition. Oxide-confined devices are already past the transition stage. We describe the generally excellent reliability of oxide-confined devices already in high-volume production, and compare it to results of the most recent-and possibly last-long-term reliability study of proton-implanted VCSELs. We report on detailed package-VCSEL interaction modeling, which is being used to improve performance and extend the life of common form-factor packages. We also note Honeywells progress toward commercialization of VCSELs and allied products at wavelengths other than 850 nm.

Reliability of proton-implanted VCSELs for data communications

We describe vertical cavity surface emitting laser (VCSEL) reliability tests comprising hundreds of parts and more than a million device hours. The VCSELs studied were of a previously described production design intended for local-area network data communication at 850 nm. Devices were operated at temperatures of 35, 80, 100, 125, and 150 degrees C and at currents of 5, 10, 15, 20, and 30 mA, and their operating characteristics were measured at room temperature. Additional groups were operated at 225 degrees C. Nominal operation is expected to be at 40 degrees C ambient and near 10mA; stresses due to temperatures and currents above the operating range accelerated degradation. The results support an Arrhenius- type failure-acceleration model with lognormal reliability distribution and lead to an 0.88-1.2- eV estimate for the failure activation energy. When tested at room temperature, typical VCSELs exhibited initial increases in power followed by decreases. The results were essentially independent of the package type (hermetic, unsealed, or overmolded plastic). Time- lapse video of degrading devices was employed in an effort to define the failure mode, which does not appear to be mediated by dark-line defects. Under normal operating conditions the observed VCSEL reliability is equal to, or better than, typical reliability results for other AlGaAs data communications lasers or LEDs.

Reliability study of 850 nm VCSELs for data communications

We present reliability results for 850 nm Vertical Cavity Surface Emitting Laser (VCSEL) devices. Hundreds of parts from multiple wafer lots and package styles were subjected to burn-in for thousands of hours at various temperatures and currents, yielding more than one million device-hours of data. Possible failure mechanisms are also discussed.

A plot twist: the continuing story of VCSELs at AOC

During a year of substantial consolidation in the VCSEL industry, Honeywell sold their VCSEL Optical Products Division, which has now officially changed its name to Advanced Optical Components (AOC). Both manufacture and applied research continue, however. Some of the developments of the past year are discussed in this paper. They include advances in the understanding of VCSEL degradation physics, substantial improvements in long-wavelength VCSEL performance, and continuing progress in manufacturing technology. In addition, higher speed serial communications products, at 10 gigabits and particularly at 4 gigabits per second, have shown faster than predicted growth. We place these technologies and AOCs approach to them in a market perspective, along with other emerging applications.

VCSELs at Honeywell: The story continues

Honeywell continues to be the world’s leading supplier of VCSELs operating at 850 nm. This paper will cover new commercial application areas for 850-nm VCSELs, and will present new findings in VCSEL reliability science. In particular, newly-developing applications drive requirements for ever more reliable VCSEL design and fabrication, and for improvements in controls for ESD (electrostatic discharge) and EOS (electrical overstress) at manufacturing facilities both for VCSEL components and for higher-level assemblies employing VCSEL components. Honeywell efforts toward improvement of reliability and toward reduction of ESD exposure are described, as is an alternative approach to improving reliability of systems containing VCSELs without compromising their performance.

Nanoscale materials characterization of degradation in VCSELs

Significant advancements have been made in the characterization and understanding of the degradation behavior of the III-V semiconductor materials employed in Vertical Cavity Surface Emitting Laser (VCSEL) diodes. Briefly, for the first time a technique has been developed whereby it is possible to view the entire active region of a solid state laser in a Transmission Electron Microscope (TEM) using a novel Focussed Ion Beam (FIB) prepared plan-view sample geometry. This technique, in conjunction with TEM cross-section imaging has enabled a three-dimensional characterization of several of the degradation mechanisms that lead to laser failure. It is found that there may occur an initial drop in laser power output due to the development of cracks in the upper mirror layers. In later stages of degradation, dislocations are punched out at stress-concentrating sites (e.g. oxide aperture tips) and these dislocations can then extend over the active region in a manner consistent with recombination enhanced dislocation motion. Alternatively, complex three-dimensional dislocation arrays which exhibited dendritic-like growth and which cover the entire active region can nucleate on a single defect.

More VCSELs at Finisar

In this paper we describe progress in moving VCSELs toward production-ready status in several applications, among others including substantially higher modulation speeds (14-25 Gbps, or even higher) than in current production. In addition we describe potential VCSEL failure mechanisms not previously published, as well as the limitations of some reliability testing techniques.

Beyond 850 nm: progress at other wavelengths and implications from the standard

Born of necessity of application, the Vertical Cavity Surface Emitting Laser (VCSEL) is now found in nearly all optical networking systems based on standards such as the IEEE 802.3z and ANSI X3.t11. Reliability continues to be the hallmark of the technology, and the volume manufacturing aspects are now realized. While VCSEls satisfying optical networking standards continue to provide the highest volume applications, the advantages of the technology are beginning to enable novel optical equipment. This paper explores development of VCSELs at wavelengths from 650 to 850nm, and the commercial applications of these devices in both the data communications and optical sensing arenas. VCSELs operating at longer wavelengths are also being developed, but are not at a stage of commercialization to be discussed in this forum.