THz Electroluminescence from Si/SiGe Quantum Cascade Heterostructures

There is an increasingly strong interest in the development of sources that emit radiation in the 1-10 THz frequency range for a number of appli cations. These include medical imaging of skin cancer (Ref-1), dental imaging (Ref. 2), telecommunications, security scanning, gas sensing, astronomy, molecular spectroscopy, and the possible detection of biological agents [Ref. 3]. While a number of THz sources are available, there are at present no compact, efficient, cheap and practical high-power solid-state sources such as light emitting diodes (LEDs) or lasers. Silicon is an excellent candidate for such a THz source as it is an inherently low loss material at these frequencies. This is mainly due to the absence of polar optical phonon scattering. Furthermore, since over 97% of all microelectronics is presently silicon based, the realisation of a silicon-based emitter could potentially allow integration with conventional silicon-based microelectronics.