Direct measurement of C-bc and C-bc versus voltage for small HBT's with microwave s-parameters for scaled Gummel-Poon BJT models

A novel method for determining the junction capacitances versus voltage in heterojunction bipolar transistors (HBT's) using s-parameters at microwave frequencies is presented. This new technique has several advantages over tr aditional approaches, which include: 1) it profiles capacitance at greater forward bias; 2) it enables the direct measurement of minimum geometry tran sistors; 3) it allows for the accurate extraction of scaled HBT model param eters with emitter length; and 4) it results in improved Dad parasitic deem bedding for accurate modeling. Both the capacitance-voltage and large-signa l HBT model results are shown.