Optically Allowed Photoluminescence from a Direct-Gap Si-Ge Superstructure on Si<sub>0.4</sub>Ge<sub>0.6</sub>
Bibliographic record
Abstract
Both Si and Ge possess an indirect band gap, which makes them very inefficient light emitters, and band gap engineering has been proposed as a way to overcome this limitation. According to the theoretical work of M. d’Avezac et al. ( Phys. Rev. Lett . 108, 027401 (2012)), a SiGe 2 Si 2 Ge 2 SiGe n superstructure on Si 0.4 Ge 0.6 should have a direct and dipole-allowed gap of 0.863 eV. Here we report on the growth of such a structure and its optical properties. Two similar samples were prepared by molecular-beam and solid-phase epitaxy. Photoluminescence (PL) spectra were obtained at low temperatures (6-25 K) with excitation at 405 and 458 nm. A strong low-energy PL quadruplet is seen, with peaks near 729, 758, 792 and 823 meV at 6 K, together with a much weaker peak at 871 MeV. The weak peak at 871 meV is assigned to the dipole-allowed direct-gap transition expected in the superstructure.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".