Thermal Generation in Depleted Si/SiGe/Si-Structures, Grown by MBE, APCVD and RTCVD and their Correlation to the Base Currents of Double Mesa HBT´s with Corresponding Blanket Epitaxial Layers

The base currents of double mesa SiGe-HBT´s at VBE=0.75 V as well as the thermal generation currents of deeply depleted MOS-structures, both grown with identical Ge-profiles, have been measured. The epilayers were deposited by MBE, RTCVD, and APCVD to compare the influence of these epitaxial techniques on the electrical parameters of the prepared HBT´s. As a preliminary result, the base currents of MBE-HBT´s and the generation currents measured at corresponding MOS-structures are found to be significantly higher compared to CVD grown structures. The very simple preparation of MOS-structures favours the used double sweep I(V)-technique for generation current determination as a useful method for optimizing the epitaxial process for HBT-preparations within rapid iteration cycles. First results of such optimizations are reported.