Abstract
The intentional merging of epitaxial Ge on Si(001) quantum dots with optically active defect sites promises low‐cost applications such as room temperature (RT) light emitters in Si photonics. Despite recent progress in this field, important benchmarks, for example, the thermal stability of such a combination of low‐dimensional nanosystems, as well as the curing of parasitic charge‐carrier recombination channels, have been barely investigated thus far. Herein, the structural robustness of defect‐enhanced quantum dots (DEQDs) is examined under millisecond flash lamp annealing (FLA), carried out at sample temperatures up to 800 °C. Changes in the optical DEQD properties are investigated using photoluminescence spectroscopy performed in a sample temperature range from 10 to 300 K. It is demonstrated that FLA—in contrast to in situ thermal annealing—leads to only negligible modifications of the electronic band alignment. Moreover, upon proper conditions of FLA, the RT emission intensity of DEQDs is improved by almost 50% with respect to untreated reference samples.
Highlights
Introduction candidate as gain material inSi-compatible light sources to be used in the field of Si photonics,[14,15] i.e., for future on- and inter-chip optical data communication as well as Thermal annealing is omnipresent in Si-based semiconductor sensing in lab-on-a-chip systems that are driven by the power of technology,[1,2,3] including processes like dopant activation and Si microelectronics.[16]
The main conclusion of this work is that we were able to demonstrate that defect-enhanced quantum dots (DEQDs) can withstand high temperatures of up to 800 C, occurring during flash lamp annealing (FLA) processes
We show that FLA—in contrast to in situ thermal annealing[12]—leads to only negligible modifications of the electronic band alignment
Summary
The defect-enhanced Ge QD samples were grown on Si(001) substrates in a Riber Siva 45 solid-source molecular beam epitaxy (MBE) system. 8.4 Å of Ge at TG 1⁄4 500 C and a growth rate of 0.05 Å sÀ1.[17] At this growth temperature, QDs of {105}-facetted and %2 nm high hut clusters with Ge concentrations close to 100% evolve on the initially grown Ge-rich wetting layer.[18,19] During the entire deposition time of Ge, Ge ions with an estimated dose of about 104 μmÀ2 were implanted into the Ge epilayer by applying a bias of À2 kV to the substrate.[10] Applying such low-energy ion implantation using heavy ions like Geþ result in ion implantation depths of 1–2 nm which was carefully adjusted to the height of the QDs.[10,12,20] This ensures that ions can stop within the formed Ge crystal and leads to beneficial optical properties of the QDs. To conclude the growth, a 70 nm thick Si capping layer was deposited at 0.6 Å sÀ1 by ramping TG from 500 to 570 C. 15 nominally identical samples were fabricated, whereas 13 were treated by FLA, and two samples were used as reference
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