Real space transfer of electrons in a Si-based quantum structure and its application to infrared generation

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Intra-band transitions hold promise in realizing light-emitting silicon in that it does not suffer from the otherwise inextricable indirect band-gap of Si. In this study, we explored real space transfer of electrons in pseudomorphic SiGe/Si heterosturctrues in an attempt to generate infrared radiation due to intersubband transitions.A cascade design is widely accepted as being representative in terms of intersubband luminescence. Quantum barriers, superlatices with tuned resonance states, however, are some of what make it arguably the state-of-the-art technology, which is highly complicated and as such not easily transplanted into the SiGe-system. A two level system consisting of the ground state of a quantum well with its potential barrier was considered here instead. Carriers will be real-space-transferred to the barrer with a low drift mobility as they are accelerated along the quantum well having a higher mobility to the point where excess kinetic energy allows relaxation to set in … More via scattering.Here we report the characteristics of real space transfer of carriers in SiGe/Si heterostructures and the attempt of light/carrier confinement based on a SiGe-OI substrate. Carrier mobilities were evaluated by optical means using a masked time-of-flight technique, which measures the ambipolar diffusivity of excitons. The diffusivity of the other of 10cm^2/s was obtained, which increased with increasing temperature while the thermal escape of carriers from the well hampered the measurement above 100K. The mobility values were not much different regardless of what constitutes the channel, SiGe or Si, which indicates that the mobility inevitably dwindled due to the roughness scattering because we had to choose a narrow width to comply with the energy ceiling of the potential barrier at a fairly large Ge content. This along with bound-state energy calculation suggests that one should target a small Ge content and a wide well or a single-heterostructure rather than quantum well. Real space transfer of electrons due to both electric biasing and phonon scattering was clearly observed in type-I SiGe/Si quantum wells, which fortuitously allowed us to develop a color-tunable light-emitter made of Si. It is also pointed out that spectroscopy of infrared generation under current injection should avoid the confusion with the background including the blackbody radiation from samples. On the other hand, a high-energy ion-implantation was found to be essential to the SiGe-OI substrate creation for the purpose of this study. Besides these, it was found through a series of luminescence experiments that the otherwise dissipative Auger recombination potentially competing with gain at an increased excitation density could be suppressed simply by implementing a SiGe/Si heterostructure. Less