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 SiGe2Si2Ge2SiGen superstructure on Si0.4Ge0.6 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.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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 source (direct Gemma or distilled Codex), 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".