Semiconductor Nanomaterials for Information and Energy Technologies

Low dimensional nanomaterials (1 D nanowires and 0 D quantum dots) represent important nanoscale building blocks with substantial potential for exploring new device concepts and materials for nanoelectronics, optoelectronics and energy technology applications. Three examples will be presented. First, I will discuss my discovery of unique rectified silver/amorphous silicon/crystalline silicon (Ag/a-Si/c-Si) crossbar resistive random access memory (RRAM) effect in c-Si/a-Si core/shell nanowires and provide a comprehensive comparison between nanowire based and planar silicon based Ag/a-Si/c-Si RRAMs. The history of how this accidental nanowire based discovery solved a decades-long sneak current problem in RRAM field and eventually evolved into a game changing mainstream flash memory successor, Crossbar Memory, will be presented. Then I will report the experimental realization of high efficiency single coaxial group III-nitride heterostructured nanowire photovoltaic devices and light emitting devices. Meanwhile, a universal van der Waals epitaxial growth strategy for compound semiconductor nanowire arrays will be discussed. The vision of how the combination of nanowire array growth and heterostructured nanowire devices could possibly change the substrate limited status of III-Nitride research fields will be outlined. Lastly, I will present how quantum dots materials innovation and novel device structure design/processing helped resolve one long standing issue for organic based light emitting devices, the efficiency roll off at high driving current density. As a result, record breaking ultrabright, highly efficient, low roll off inverted red quantum dot light emitting devices (QLEDs) have been achieved (165,000Cd/m2 at <6V driving voltage). Strategies to attack the only remaining issue (long term instability) of QLEDs will be discussed in the end.