TY - GEN
T1 - Electron emission from deep traps in hydrogenated amorphous silicon and silicon-germanium
T2 - 2011 MRS Spring Meeting
AU - Long, Qi
AU - Dinca, Steluta
AU - Schiff, Eric A.
AU - Yan, Baojie
AU - Yang, Jeff
AU - Guha, Subhendu
N1 - Funding Information:
Trap emission prefactor frequencies for many amorphous silicon type materials are often in the range 1011-1013 s-1, which is similar to the fundamental Eyring frequency. In this paper we've shown that a much larger range of prefactors (109) has been measured, including some very large values in device-grade materials. There is a fairly good "Meyer-Neldel" correlation with the emission activation energy, which likely reflects "multi excitation entropy" of phonons. A less familiar aspect is the enormous ionization entropy implied by the Meyer-Neldel graph for dangling bond emission when compared with related processes such as bandtail trap emission. We are not aware of any satisfactory explanation for this aspect of the measurements. This research has been supported by the U. S. Department of Energy through the Solar America Initiative (DE-FC36-07 GO 17053). Additional support was received from the Empire State Development Corporation through the Syracuse Center of Excellence in Environmental and Energy Systems.
PY - 2012
Y1 - 2012
N2 - We have measured electron drift in amorphous silicon-germanium nip photodiodes using the photocarrier time-of-flight technique. The samples show electron deep-trapping shortly after photogeneration, which is generally attributed to capture by a neutral dangling bond (D 0) to form a negatively charged center (D -). An unusual feature is that electron re-emission from the trap is also clearly seen in the transients. Temperature-dependent measurements on the emission yield an activation energy of about 0.8 eV and the remarkably large value of 10 15 Hz for the emission prefactor frequency. We also compiled results on electron emission from deep traps in a-Si:H, a-SiGe:H, and a-SiC:H from six previous publications. Collectively, these measurements exhibit "Meyer Neldel" behavior for electron emission over a range of activation energies from 0.2-0.8 eV and a prefactor range extending over nine decades, from 10 6 to 10 15 Hz. The Meyer-Neldel behavior is consistent with the predictions of the multi-excitation entropy model. We extract a ionization entropy of 20k B from the measurements, which is very large compared to crystal silicon. We discuss this result in terms of a bond charge model.
AB - We have measured electron drift in amorphous silicon-germanium nip photodiodes using the photocarrier time-of-flight technique. The samples show electron deep-trapping shortly after photogeneration, which is generally attributed to capture by a neutral dangling bond (D 0) to form a negatively charged center (D -). An unusual feature is that electron re-emission from the trap is also clearly seen in the transients. Temperature-dependent measurements on the emission yield an activation energy of about 0.8 eV and the remarkably large value of 10 15 Hz for the emission prefactor frequency. We also compiled results on electron emission from deep traps in a-Si:H, a-SiGe:H, and a-SiC:H from six previous publications. Collectively, these measurements exhibit "Meyer Neldel" behavior for electron emission over a range of activation energies from 0.2-0.8 eV and a prefactor range extending over nine decades, from 10 6 to 10 15 Hz. The Meyer-Neldel behavior is consistent with the predictions of the multi-excitation entropy model. We extract a ionization entropy of 20k B from the measurements, which is very large compared to crystal silicon. We discuss this result in terms of a bond charge model.
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U2 - 10.1557/opl.2011.1229
DO - 10.1557/opl.2011.1229
M3 - Conference contribution
AN - SCOPUS:84455212223
SN - 9781605112985
T3 - Materials Research Society Symposium Proceedings
SP - 329
EP - 334
BT - Amorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2011
Y2 - 25 April 2011 through 29 April 2011
ER -