In 2007 Finisar® completed the transfer of an entire epitaxial and fabrication line from one facility to another. During
this period, reliability models had to be re-validated and product continuity maintained. In this paper we describe the
activities necessary to support such a transition, and we extend previously published VCSEL failure atlases.
After some thirty years of materials analyses into the failure behavior of III-V semiconductor lasers, manufacturers of these devices still regularly encounter new failure mechanisms. This is due mainly to the implementation of progressively more complex and refined designs in devices that are, moreover, often subjected to increasingly more stressful operating or environmental conditions. It is therefore incumbent upon commercial laser manufacturers to maintain a persistent effort to search out and understand these new failure mechanisms, preferably before they are uncovered by an unhappy customer. Below, we describe our pursuit of a thorough materials-level understanding of VCSEL behaviors and illustrate some of the positive effects of these efforts.
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 AOC's approach to them in a market perspective, along with other emerging applications.
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.
In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been demonstrated to 1338 nm lasing at temperatures up to 90 C. Continuous wave InP based 1550 nm VCSELs have also been demonstrated.
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.
We examine the threshold characteristics of selectively oxidized VCSELs as a function of the number, thickness, and placement of the buried oxide apertures. The threshold current density for small area VCSELs is shown to increase with the number of oxide apertures in the cavity due to increased optical loss, while the threshold current density for broad area VCSELs decreases with increasing number of apertures due to more uniform current injection. Reductions of the threshold gain and optical loss are achieved for small area VCSELs using thin oxide apertures which are displaced longitudinally away from the optical cavity. We show that the optical loss can be sufficiency reduced to allow lasing in VCSELs with aperture area as small as 0.25 micrometer<SUP>2</SUP>.