Physical mechanism for saturation of persistent photoconductivity in a GaAs–AlAs/GaAs single heterojunction
Bibliographic record
Abstract
The saturation in persistent photoconductivity (PPC) in a Si-doped GaAs–AlAs/GaAs heterostructure is investigated using magnetotransport technique at 4.2 K. Against the donor density of 1.2×1013 cm−2, the maximum electron concentration including the contribution from the two-dimensional channel after 1.41 eV illumination is found to be 7.9×1011 cm−2. This result is anomalous as the DX states are expected to respond to 1.41 eV photons so as to bring the electron density close to the donor density. In order to investigate this issue a high electron-mobility transistor has been fabricated. The channel of this device contains a Hall-bridge pattern. The capacitance–voltage in conjunction with quantum transport measurements reveals that at saturation of PPC a second channel of electron gas is present in GaAs–AlAs superlattice. Furthermore, this channel is a nonconducting one as the electrons in it do not participate in the transport process. The reason behind it is the presence of potential barriers that separate the electron gas in the superlattice (EGS) from the alloyed regions meant for ohmic contacts to two-dimensional electron gas (2DEG). The formation of these potential barriers is linked to the lateral diffusion of In atoms used to make ohmic contacts to 2DEG. At saturation of PPC the electron density of EGS and 2DEG together is found to be 2.2×1012 cm−2. The remaining donors are believed to form electronically inactive complexes. At saturation of PPC the two-dimensional electron density (n2D) is determined by the tunneling probability through the potential barrier adjacent to the alloyed region. During the course of this investigation n2D at 4.2 K measured in the dark was found to depend on the cooldown rate. This phenomenon is attributed to the formation of a nonconducting channel.
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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 | 0.000 | 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".