Highly-Strained P-type Modulation Doped Active Regions for High-Speed VCSELs.

摘要

In the age of ubiquitous computing, we are never far from the data we need and even the ones we don't. To support this constant stream of information, large central facilities called data centers are used to process, route and store the data before it beaming it to your favorite device. The bottleneck for these sprawling data centers lie in the movement of data from one point to another and at increasingly higher speeds. The traditional network of copper wires is currently at odds with growth trends because they must be shortened to achieve the necessary higher speeds while data centers are only getting larger. A far more promising solution is to transmit data through fiber optical cables using high-speed vertical cavity surface emitting lasers (VCSELs) which can operate at higher speeds, use less energy, and can be built at low-cost. In this dissertation I demonstrate for the first time, the simultaneous use of p-type modulation doping in highly-strained 1060 nm QW VCSELs to simultaneously achieve high differential gain and low damping which increases the intrinsic bandwidth from 23 to 43 GHz. Additionally, the separate confinement heterostructure (SCH) surrounding the active region is adjusted to decrease the accumulation of carriers through the growth of graded heteorjunctions which ultimately reduces electrical parasitics. Optimized growth techniques for low resistance p-DBR mirrors are also shown as a means to reduce parasitics. I will also demonstrate a method for extending the single mode operating current range by scaling down device size to induce mode-selective loss. With these enhancements the VCSELs presented here are able to achieve 25 Gbps operation which is faster than the current 10 Gbps standard. Moreover, these lasers required only 400 fJ/bit at this data rate which is far below the commonly accepted 1 pJ/bit optical interconnects feasibility target.