Quasi-Steady-State Free Carrier Absorption Measurements of Effective Carrier Lifetime in Silicon
Bibliographic record
Abstract
The paper presents a semiconductor carrier lifetime measurement technique, quasi-steady-state free carrier absorption (QSS-FCA), that is an all-optical analog of the quasi-steady-state photoconductivity technique. The effective electron-hole recombination lifetime of silicon is measured under quasi-steady-state conditions using an above-bandgap pump and a below-bandgap probe of the free carrier absorption (FCA). A mathematical model is developed to relate the experimentally measured probe signal to the lifetime. QSS-FCA is calibrated self-consistently by measuring the quasi-steady-state signal simultaneously with the true recombination lifetime in the same apparatus. This directly establishes the relationship between the quasi-steady-state signal and lifetime, ensuring the accuracy of QSS-FCA measurements. The calibration constant is the FCA cross section of silicon, which is a material constant. QSS-FCA is a simplification of traditional FCA lifetime measurement approaches where the lifetime is extracted from a time- or frequency-resolved carrier decay. Both of these approaches require a bandwidth commensurate with the inverse carrier lifetime of the wafer and require fitting multiple data points in order to extract the lifetime. In contrast, QSS-FCA is a quasi-steady-state measurement, so it is inherently low frequency, and as a single point measurement technique, fitting is not required. Finally, since QSS-FCA is a purely optical technique, it opens up the possibility of in situ lifetime characterization that would be inaccessible to the traditional RF/microwave-based lifetime measurement techniques.
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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 | 0.001 | 0.001 |
| 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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".