The determination of valence band discontinuities in Si/Si _1-xGe_x/Si heterojunctions by capacitance-voltage techniques

Capacitance-voltage (C-V) profiling has been used to measure the apparent carrier concentration profiles in Si/Si_1-xGe_x/Si structures for a range of Ge percentages. Using Kroemers analysis, good agreement has been found between theoretical valence band offsets and those determined from the experimental data. The validity of Kroemers analysis has been assessed in the presence of traps using a C-V simulation program. Under certain circumstances, large errors occur in the extracted valence band offset due to distortion of the apparent carrier concentration profile by traps. It is proposed that the experimental data presented here falls into a regime where minimal distortion is to be expected and is reflected by the accuracy of the extracted valence band offsets.