High resolution photoluminescence spectroscopy of donors in undoped and In-doped ZnO grown by metalorganic vapor phase epitaxy
Bibliographic record
Abstract
We report the observation of photoluminescence (PL) transitions in ZnO epilayers grown by metalorganic vapor phase epitaxy (MOVPE) on C-sapphire substrates with linewidths as low as 0.2 meV at 4.2 K. A dominant donor bound exciton (D0X) peak at 3361.0 meV is observed in all undoped samples together with the corresponding ionized donor bound exciton (D+X) peak at 3372.9 meV. The addition of In dopant using trimethylindium results in the appearance of the I9 transition at 3357.8 meV, which has been previously attributed to In D0X transitions. By intentionally doping the epilayers with In we can calibrate the PL energy spectra, and thereby identify the dominant D0X transition in undoped material at 3361.0 meV as due to Ga donors. The In and Ga identifications are also confirmed by the observation of two electron satellites. High temperature annealing under O2 results in a strong reduction of the In and Ga transitions, and the appearance of a third line which we attribute to Al out-diffusing from the sapphire substrate. Temperature dependent PL measurements on In-doped samples above 4 K show additional lines due to well-resolved D0X (B) transitions separated by 4.6 meV for both Ga and In donors due to the crystal field splitting of the valence band. The line intensities are modeled by simple Boltzmann statistics. On the basis of comparison with accepted values of the I9 transition energy in homoepitaxial ZnO samples, we deduce a strain-induced blueshift of ∼ 1.2 meV which is consistent with residual compressive strain induced in the ZnO films due to the smaller in-plane effective lattice constant of sapphire.
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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) | 0.000 | 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) | 0.000 | 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 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".