SI1-XGEX SI VALENCE-BAND OFFSET DETERMINATION USING CURRENT-VOLTAGE CHARACTERISTICS/

The valence band offset (Delta E-v) between strained Si1-xGex and Si c an be determined by temperature-dependent current-voltage (I-V-T) meas urements on Si/Si1-xGex/Si quantum wells (QW) using two kinds of conta cts. Firstly, we used samples with ohmic contacts and with a simple th eory of thermionic emission we estimated Delta E-v = 147 +/- 10 meV fo r x = 0.17 and Delta E-v = 190 +/- 10 meV for x = 0.22. Secondly, we i nvestigated samples with Schottky contacts. The forward I-V-T characte ristics show a normal Schottky diode behavior up to 0.5 V, Then the sl ope decreases strongly at higher voltages. This behavior was attribute d to the effect of an additional barrier due to the band offset betwee n Si and Si1-xGex at the QW. From these measurements we estimated Delt a E-v = 105 +/- 20 meV for x = 0.17 and Delta E-v = 190 +/- 20 meV for x = 0.22. It is shown that the Delta E-v evaluated on samples with oh mic contacts an more reliable.