CHARACTERIZATION OF AN N-TYPE SI SIGE MODULATION-DOPED FIELD-EFFECT TRANSISTOR/

High transconductance n-type Si/SiGe modulation doped field-effect tra nsistors (MODFETs) are fabricated and characterised using a charge con trol model. The electron saturation velocity, the low field mobility a nd the equilibrium carrier concentration of the two-dimensional electr on gas in the channel are derived from the characterisation. These val ues are used for the calculation of the MODFET transconductance for de vices with different gate lengths and gate-to-channel distances. Trans conductances of 130 mS mm(-1) and 310 mS mm(-1) are measured for MODFE Ts with 0.5 mu m gate length having 24 nm and 4 nm gate-to-channel dis tances, respectively. Calculated values of transconductances are in go od agreement with these measured data. Estimated upper limit of transc onductance for very short gate MODFETs based on characterised SiGe het erostructure is 1020 mS mm(-1). (C) 1997 Elsevier Science S.A.