Impact ionization and high-field transport in semiconductors

Aspects of high field transport related to hot electron reliability effects are investigated--with special emphasis, the phenomenon of impact ionization. Both the ionization rate itself and its effect on bulk semiconductor transport are computed by a full-band Monte Carlo algorithm for Si and several III-V materials. Furthermore, a new interpretation of hot carrier luminescence spectra is given which can explain important features of hot electron distribution functions in MOSFETs.Our theory of impact ionization in semiconductors expands an earlier theory of Kane and includes the effects of high electric fields and high scattering rates on the electron-electron collision process. It is shown that their combined effect, i.e., the intracollisional field effect and collision broadening, leads to a softening of the threshold energy for impact ionization and a marked increase in the anisotropy of the ionization rate with respect to the direction of the electric field. Ionization rates are presented for Si, GaAs, InP, InAs, and Ga$\sb{0.43}$In$\sb{0.57}$As. Using these ionization rates, several prejudices concerning impact ionization are re-examined and a new view of the role of thresholds is offered. Trends of ionization coefficients related to the energy band structure for these compounds are also discussed.Finally, a new computational model for the physical mechanisms of light emission in Si under various doping and carrier densities is developed with incorporates various hot carrier distribution function models. Our model includes a realistic band structure which is essential to the study of hot carrier luminescence in Si. Furthermore, by including these band structure effects, it is shown that the dominant light emission mechanism in normally biased Si MOSFETs is a combination of direct and phonon-assisted inter-conduction band radiation.U of I OnlyETDs are only available to UIUC Users without author permissio