Theory and design of quantum cascade lasers in (111) n-type Si/SiGe

Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering,University of Leeds, Leeds LS2 9JT, United Kingdom(Dated: July 11, 2011)Although most work towards the realization of group IV quantum cascade lasers (QCLs) hasfocused on valence band transitions, there are many desirable properties associated with the con-duction band. We show that the commonly cited shortcomings of n-type Si/SiGe heterostructurescan be overcome by moving to the (111) growth direction. Specifically, a large band offset and loweffective mass are achievable and subband degeneracy is preserved. We predict net gain up to latticetemperatures of 90K in a bound-to-continuum QCL with a double-metal waveguide, and show thata Ge interdiffusion length of at least 8˚A across interfaces is tolerable.

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