RECOMBINATION MECHANISMS VIA DEEP LEVELS IN RTCVD SI SI0.85GE0.15/SI DOUBLE HETEROSTRUCTURES/

Electrical characterizations of Si/SiGe/Si double heterostructures gro wn by rapid thermal chemical vapour deposition (RTCVD) are carried out to determine the origin of the photoluminescence (PL) intensity decay at low growth temperature (T-G). For the sample grown at the highest T-G, capacitance-voltage measurements show an excellent interface carr ier confinement, while deep-level effects are not detected. For the sa mple grown at the lowest T-G, carrier confinement is less efficient an d deep-level transient spectroscopy indicates the presence of both poi nt and extended defects. The apparent activation energy of the deep le vel related to point defects is close to the heterostructure midgap (E -a = E-v + 0.47 eV). As is shown, the deep level induces an effective non-radiative lifetime of carriers in the SiGe layer which is actually responsible for the SiGe layer photoluminescence degradation at low g rowth temperatures.