This paper reports initial the demonstration of prototype Ge1-x-ySixSny light emitting diodes with distinct direct and indirect edges and high quality I-V characteristics. The devices are fabricated on Si (100) wafers in heterostructure pin geometry [n-Ge/i-Ge1-x-ySixSny/p-Ge(Sn/Si)] using ultra low-temperature (T < 300 °C) depositions of the highly reactive chemical sources Si4H10, Ge4H10, Ge3H8, and SnD4. The Sn content in the i-Ge1-x-ySixSny layer was varied from ∼3.5% to 11%, while the Si content was kept constant near 3%. The Si/Sn amounts in the p-layer were selected to mitigate the lattice mismatch so that the top interface grows defect-free, thereby reducing the deleterious effects of mismatch-induced dislocations on the optical/electrical properties. The spectral responsivity plots of the devices reveal sharp and well-defined absorption edges that systematically red-shift in the mid-IR from 1750 to 2100 nm with increasing Sn content from 3.5% to 11%. The electroluminescence spectra reveal strong direct-gap emission peaks and weak lower energy shoulders attributed to indirect gaps. Both peaks in a given spectrum red-shift with increasing Sn content and their separation decreases as the material approaches direct gap conditions in analogy with binary Ge1-ySny counterparts. These findings-combined with the enhanced thermal stability of Ge1-x-ySixSny relative to Ge1-ySny and the observation that ternary alloy disorder does not adversely affect the emission properties - indicate that Ge1-x-ySixSny may represent a practical target system for future generations of group-IV light sources on Si.
ASJC Scopus subject areas
- General Physics and Astronomy