Accession Number : ADA506386


Title :   Semiconductor Terahertz Technology


Descriptive Note : Final rept. 12 Apr 2007-15 Apr 2009


Corporate Author : MASSACHUSETTS UNIV BOSTON


Personal Author(s) : Sun, Gregory


Full Text : http://www.dtic.mil/get-tr-doc/pdf?AD=ADA506386


Report Date : 15 JUN 2009


Pagination or Media Count : 19


Abstract : During this contract, we have investigated the THz laser source based on group-IV elements and their alloys that can be developed on Si substrates. The design work focused on the structure of the so-called quantum cascade laser (QCL). Specifically, we designed a Ge/Ge0.076Si0.19Sn0.05 QCL using intersubband transitions at L-valleys of the conduction band which has a "clean" offset of 150meV situated below other energy valleys (Gamma, Chi). The entire structure is strain free because the lattice-matched Ge and Geo.76Si0.19Sn0.05 layers are to be grown on a relaxed Ge buffer layer on a Si substrate. Longer lifetimes due to the weaker scattering of nonpolar optical phonons reduce threshold current and potentially lead to room temperature operation. For the work on phonon waveguides, we have studied the characteristics of waveguides using interface phonon polaritons to confine far-infrared radiation within a sub-wavelength semiconductor layer. We have identified spectral operating regions within the Restrahlen band of a cladding layer that offers advantages over both traditional dielectric and metal clad waveguides. We showed that proposed waveguides can be used for far infrared low-threshold QCLs. The report is divided into two parts, one for the design of group-IV QCLs and the other for the phononic waveguides.


Descriptors :   *GERMANIUM , *SUBSTRATES , *PHONONS , *WAVEGUIDES , *TIN , *SILICON , FAR INFRARED RADIATION , CONDUCTION BANDS , GOLD , SEMICONDUCTORS , QUANTUM WELLS , QUANTUM THEORY , THRESHOLD EFFECTS , CLADDING , BUFFERS , POLARIZATION


Subject Categories : ELECTRICAL AND ELECTRONIC EQUIPMENT
      LASERS AND MASERS
      SOLID STATE PHYSICS


Distribution Statement : APPROVED FOR PUBLIC RELEASE