Physical mechanism of secondary-electron emission in Si wafers

CMOS-compatible RF/microwave devices, such as filters and amplifiers, have been widely used in wireless communication systems. However, secondary-electron emission phenomena often occur in RF/microwave devices based on silicon (Si) wafers, especially in the high-frequency range. In this paper, we have studied the major factors that influence the secondary-electron yield (SEY) in commercial Si wafers with different doping concentrations. We show that the SEY is suppressed as the doping concentration increases, corresponding to a relatively short effective escape depth λ. Meanwhile, the reduced narrow band gap is beneficial in suppressing the SEY, in which the absence of a shallow energy band below the conduction band will easily capture electrons, as revealed by first-principles calculations. Thus, the new physical mechanism combined with the effective escape depth and band gap can provide useful guidance for the design of integrated RF/microwave devices based on Si wafers.