NanoScience Colloquium by Prof Jani Oksanen

Diffusion plays a critical role in both electronics and optoelectronics, influencing how charge carriers and dopants behave in semiconductor materials. It is essential for the operation of LEDs and solar cells and can also enable other energy conversion processes.

In this talk I will overview the role of diffusion in selected semiconductor devices, and introduce our group's activities touching on the topic. In particular I will discuss the role of drift and diffusion, and how to harness diffusion to create new (and old) types of devices and energy converters; For LEDs diffusion driven devices can be expected to provide very low resistive losses and enable fully back contacted devices leading to very high efficiency LEDs, ideally breaking thermodynamic barriers converting LEDs into optical refrigerators. Some of these prospects also apply to III-V solar cells, and even to new types of elecrochemical energy converters. While the possibilities or diffusion driven devices especially in optoelecronics are substantial, fabrication of optimal devices sets new requirements for device dimensions and calls for fabrication methods that have not been readily available for III-V materials.