Abstract

Electrically-injected group-IV light emitters on silicon are a crucial element for silicon photonics [1]. The challenge to realize efficient group-IV light emitters is the indirectness of the band structure in conventional group-IV semiconductors including Si, Ge, and their alloys. Forth-nately, Ge is a quasi-direct bandgap material in which the direct conduction band lies just 136.5 meV above the lowest conduction band at the L-valley. One viable approach to enhance the light emitting efficiency of Ge is the add Sn, another group-IV element, into Ge to form GeSn alloys. With a Sn content of ~7%, GeSn alloys can be transferred into direct bandgap material for developing efficient group-IV light emitters. With the development of low-temperature growth techniques, high-Sn-content GeSn layers can be directly grown on Si or SOI substrates, leading to the realization of optically-pumped GeSn lasers [2]. However, to be useful for silicon photonics, electrically-injected GeSn layers are highly desired. Recently, electrically-injected GeSn lasers have been experimentally demonstrated with a lasing temperature up to 100 K, showing great promises for efficient group-IV light emitters [3].

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