Si/SiGe epitaxial-base transistors. I. Materials, physics, and circuits

Influence of alloy inhomogeneities on the determination by Raman scattering of composition and strain in Si1–xGex/Si(001) layers

“…4 as solutions of the system given by Eqs. (8) and (9) for all the as-grown samples (solid lines) and the fully annealed ones (lines inside circular marks). The dotted lines represent contour plots for different values of R, though calculated only for the as-grown samples.…”

“…Larger carrier mobilities, 1,2 higher device-switching speeds, [3][4][5] and lower power consumption 6 are some of the advantages that make strained SiGe/Si structures a good alternative to their already well established counterpart. Successful inclusion of Ge in a great variety of device architectures such as heterojunction bipolar transistors [7][8][9] (HBTs), metal-oxide-semiconductor field-effect transistors [10][11][12] (MOSFETs), and optical modulators 13,14 has been already clearly demonstrated. The advantages offered by this material system partly originate from the larger carrier mobilities 1 exhibited by Ge (l e ¼ 3900 cm 2 /Vs, l h ¼ 1800 cm 2 /Vs) as compared to Si (l e ¼ 500 cm 2 /Vs, l h ¼ 1450 cm 2 /Vs).…”

Influence of Fermi-Dirac Statistics on Collector Current of npn SiGe HBT at Low Temperatures

“…Since AEg,Ge,G is approximately linear function of Ge fraction, an effective trapezoidal Ge profile can be found for every grown trapezoidal Ge profile, doping concentration in the base and temperature (Fig.4b). Since the trapezoidal Ge profile can be treated analytically [2,4], the collector current in SiGe HBT with degenerately doped base and trapezoidal Ge profile can be modelled analytically by means of AE,,@ In this approach it is necessary to evaluate AE8,Ge,@ only at both edges of the base. The collector current then reads: The ratio of approximated collector current (eq.…”

“…(3) cannot be solved analytically without simplifications (integral of exp(G,,J in (3) cannot be solved analytically). An analytical expression for I, in the case of B statistics (AEDos,, and AE,, are neglected) was presented in [4], where position averaged quantities of AEDOS,, and D,,, were introduced and exp(-AE,,JkT) was integrated.…”

“…Since the doping concentration in the base of SiGe HBTs operating at low temperatures should be high enough to prevent carrier freeze-out and to assure low base resistance, FD statistics instead of Boltzmann (B) statistics should be taken into consideration for analysis and optimization of low temperature base transport properties of SiGe HBTs. Existing analytical expressions for the collector current (Ic,,,,) and related properties of SiGe HBTs are generally based on B statistics [1, 2,4]. For this reason such expressions seem not to be appropriate for low-temperature analyses of SiGe HBTs [1,2].…”