Fischetti, Massimo V.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2310
An expert in how electrons move in solids, Dr. Fischetti is renowned in the field for the development of DAMOCLES, a computer program that was the first to accurately simulate how electrons move in small semiconductors using what is known as the Monte Carlo transport model. The program is used to design transistors for chips in computers, smartphones and advanced video games.
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Browsing Fischetti, Massimo V. by Subject "Electron impact ionization"
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Item Fundamental Limitations of Hot-Carrier Solar CellsKirk, Alexander P.; Fischetti, Massimo V.Sunlight-generated hot-carrier transport in strongly absorbing direct band-gap GaAs-among the most optimal of semiconductors for high-efficiency solar cells-is simulated with an accurate full-band structure self-consistent Monte Carlo method, including short- and long-range Coulomb interaction, impact ionization, and optical and acoustic phonon scattering. We consider an ultrapure 100-nm-thick intrinsic GaAs absorber layer designed with quasiballistic carrier transport that achieves complete photon absorption down to the band edge by application of careful light trapping and that has a generous hot-carrier retention time of 10 ps prior to the onset of carrier relaxation. We find that hot-carrier solar cells can be severely limited in performance due to the substantially reduced current density caused by insufficient extraction of the widely distributed hot electrons (holes) through the requisite energy selective contacts. © 2012 American Physical Society.Item "Hot Electrons in Si Lose Energy Mostly to Optical Phonons:" Truth or Myth?(American Institute of Physics Inc., 2019-06-05) Fischetti, Massimo V.; Yoder, P. D.; Khatami, Mohammad Mahdi; Gaddemane, Gautam; Van De Put, Maarten L.; 0000-0001-5926-0200 (Fischetti, MV); 0000-0003-0067-8674 (Gaddemane, G); 0000-0001-8014-0350 (Khatami, MM); 0000-0001-9179-6443 (Van de Put, ML); Fischetti, Massimo V.; Khatami, Mohammad Mahdi; Gaddemane, Gautam; Van De Put, Maarten L.Theoretical studies of heat generation and diffusion in Si devices generally assume that hot electrons in Si lose their energy mainly to optical phonons. Here, we briefly review the history of this assumption, and using full-band Monte Carlo simulations - with electron-phonon scattering rates calculated using the rigid-ion approximation and both empirical pseudopotentials and Harris potentials - we show that, instead, electrons lose as much as 2/3 of their energy to acoustic phonons. The scattering rates that we have calculated have been used to study hot-electron effects, such as impact ionization and injection into SiO2, and are in rough agreement with those obtained using density functional theory. Moreover, direct subpicosecond pump-probe experimental results, some of them dating back to 1994, are consistent with the predictions of our model. We conclude that the study of heat generation and dissipation in nanometer-scale Si devices may require a substantial revision of the assumptions that have been considered "common wisdom" so far. © 2019 Author(s).Item Understanding the Average Electron-Hole Pair-Creation Energy in Silicon and Germanium Based on Full-Band Monte Carlo Simulations(Institute of Electrical Electronics Engineers Inc, 2019-01) Fang, Jingtian; Reaz, Mahmud; Weeden-Wright, Stephanie L.; Schrimpf, Ronald D.; Reed, Robert A.; Weller, Robert A.; Fischetti, Massimo V.; Pantelides, Sokrates T.; 0000-0001-5926-0200 (Fischetti, MV); Fischetti, Massimo V.The thermalization process of sub-10-eV charge carriers is examined with treating carrier transport with full-band Monte Carlo simulations. The average energy loss (3.69 eV in Si and 2.62 eV in Ge) required to create a thermalized electron-hole pair, obtained from the simulations, is very close to the experimentally measured radiation-ionization energies of Si and Ge irradiated with high-energy particles. These results suggest that only interactions that occur after the radiation-generated charge carriers decay to energies of similar to 10 eV or less determine the fundamental property of the radiation-ionization energies. In addition to an energy loss equal to the band gap energy via impact ionization, acoustic-phonon emission, which has been omitted in prior work, contributes 30% of the remaining carrier energy loss, while optical-phonon emission contributes the other 70%.