Metronik (Slovenia)

Modeling of effective densities of states N V,SiGe in heterojunction bipolar transistor is presented, based on accurate determination of hole effective mass m p * . Algorithm for calculation of hole effective mass m p * is presented, which is optimized for numerical device modeling. Corresponding Fortran subroutine named HEM is discussed, which calculates hole effective mass in the temperature range of T=77K-300K, base doping level bellow 10 20 cm -3 and germanium content x Ge =0,00-0,30. Finally, Fortran subroutine HEM is incorporated into numerical device simulator MEDICI and tested through simulation of idealized heterojunction bipolar transistor.

Based on theoretical and experimental studies of band tails in silicon found in the literature, the influence of band tails on electrical properties of p-type SiGe is analyzed. The consideration of the band tail influence for the purposes of device modeling is suggested. The relationship between band tails and apparent bandgap narrowing is discussed. The proposal for experimental validation of effective bandgap shift due to band tails is given.