Nanopillars for bandgap-engineering in III-V optoelectronic devices

The absorption or emission wavelength in optoelectronic devices such as quantum well infrared photodetectors, quantum cascade lasers, and type II superlattice photodiodes can be controlled by the thickness and composition of the quantum wells that constitute their active layers. By further confining the charge carriers, for instance in a quantum dot, even more control can be gained over energy transitions within the semiconductor crystal. We propose a method for manipulating the semiconductor band structure by confining carriers within nanopillar structures. Using electron beam lithography and dry plasma etching, we can precisely control the pillar placement, density and dimensions, and thus the performance characteristics, of the optoelectronic device. Furthermore, by patterning different size structures, it is possible to create arrays of multi-color devices on the same substrate, a technique that lends itself to large-scale monolithic integration. We demonstrate the fabrication of nanopillar arrays in the GaSb, GaInP, GaInAs, and type II InAs/GaSb superlattice material systems and show initial photoluminescence data, which seems to indicate quantum confinement within these structures.