期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 108, 期 47, 页码 18893-18898出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1107968108
关键词
luminescence; strain engineering; band structure
资金
- National Science Foundation [DMR-0907296]
- Department of Energy [DE-FG02-03ER46028]
- National Science Foundation
- National Defense Science and Engineering
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0907296, 0906930] Funding Source: National Science Foundation
Silicon, germanium, and related alloys, which provide the leading materials platform of electronics, are extremely inefficient light emitters because of the indirect nature of their fundamental energy bandgap. This basic materials property has so far hindered the development of group-IV photonic active devices, including diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Here we show that Ge nanomembranes (i.e., single-crystal sheets no more than a few tens of nanometers thick) can be used to overcome this materials limitation. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy bandgap relative to the indirect one. We demonstrate that mechanically stressed nanomembranes allow for the introduction of sufficient biaxial tensile strain to transform Ge into a direct-bandgap material with strongly enhanced light-emission efficiency, capable of supporting population inversion as required for providing optical gain.
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