The progress towards terahertz quantum cascade lasers on silicon substrates

A review is presented of work over the last 10 years which has been aimed at trying to produce a Si-based THz quantum cascade laser. Potential THz applications and present THz sources will be briefly discussed before the materials issues with the Si/SiGe system is discussed. Waveguide designs and waveguide losses will be presented. Experimental measurements of the non-radiative lifetimes for intersubband transitions in Si1-xGex quantum wells will be presented along with theory explaining the important scattering mechanisms which determine the lifetimes. Examples of p-type Si/SiGe quantum cascade designs with the experimental electroluminescence will be reviewed and examples of n-type Si-based designs will be presented. In the conclusion designs and structures will be discussed with the greatest potential to achieve an electrically pumped Si-based THz laser.