Progress toward silicon-based intersubband lasers

Design results are presented for the quantum parallel laser (QPL) at 1-20 mu m wavelengths and the cryogenic 4-20 mu m quantum cascade laser (QCL), For 1-2 mu m lasing, the optimum multiple quantum well heterostructures are Si quantum wells (QWs) confined by wide-gap lattice-matched semiconductor layers, especially the Si/ZnS, Si/BeSeTe, Si/gamma-Al2O3, Si/CeO2, and Si/SiOx systems (SiOx is a crystalline suboxide). The electrically pumped 300 K unipolar p-i-p. QPL consists of tightly coupled QWs exhibiting coherent transport of carriers on superlattice (SL) minibands. A good QPL candidate is the symmetrically strained Ge-n-Si-n SL grown on relaxed Si0.5Ge0.5. Local-in-k population inversion is engineered between two valence minibands. Our calculations indicate that the p-i-p QCL is feasible in Ge-Si or in lattice-matched Si0.63Ge0.33C0.04/Si The oscillator strength f(z) = 0.1 calculated for the 8 ML x 8 ML Si/ZnS zone-folded SL is insufficient for 1.1 mu m band-to-band lasing; however, the in-plane dispersion of Si QWs in Si/ZnS SLs shows valence subbands that are sufficiently nonparabolic for local-in-k lasing in QPLs and QCLs. (C) 1998 American Vacuum Society.