Indirect to Direct Band Gap Transformation by Surface Engineering in Semiconductor Nanostructures.

Indirect band gap semiconductor materials are routinely exploited in photonics, optoelectronics, and energy harvesting. However, their optical conversion efficiency is low, due to their poor optical properties, and a wide range of strategies, generally involving doping or alloying, has been explored to increase it, often, however, at the cost of changing their material properties and their band gap energy, which, in essence, amounts to changing them into different materials altogether. A key challenge is therefore to identify effective strategies to substantially enhance optical transitions at the band gap in these materials without sacrificing their intrinsic nature.