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Full-Text Articles in Physical Sciences and Mathematics
Electron Tunneling In A Strained N-Type Si1−Xgex/Si/Si1−Xgex Double-Barrier Structure, K. M. Hung, T. H. Cheng, W. P. Huang, K. Y. Wang, H. H. Cheng, Greg Sun, R. A. Soref
Electron Tunneling In A Strained N-Type Si1−Xgex/Si/Si1−Xgex Double-Barrier Structure, K. M. Hung, T. H. Cheng, W. P. Huang, K. Y. Wang, H. H. Cheng, Greg Sun, R. A. Soref
Physics Faculty Publications
We report electrical measurements on an n-type Si1−xGex/Si/Si1−xGex double-barrier structure grown on a partially relaxed Si1−yGey buffer layer. Resonance tunneling of Δ4band electrons is demonstrated. This is attributed to the strain splitting in the SiGe buffer layer where the Δ4 band is lowest in energy at the electrode. Since the Δ4 band electrons have a much lighter effective mass along the direction of tunneling current in comparison with that of the Δ2 band electrons, this work presents an advantage over those …
Observation Of Type-I And Type-Ii Excitons In Strained Si/Sige Quantum-Well Structures, K. Y. Wang, W. P. Huang, H. H. Cheng, Greg Sun, R. A. Soref, R. J. Nicholas, Y. W. Suen
Observation Of Type-I And Type-Ii Excitons In Strained Si/Sige Quantum-Well Structures, K. Y. Wang, W. P. Huang, H. H. Cheng, Greg Sun, R. A. Soref, R. J. Nicholas, Y. W. Suen
Physics Faculty Publications
The authors report photoluminescence (PL) measurement on a series of Si/SiGequantum-well structures that had different internal strain distributions. When each sample was placed in a high magnetic field, the field-dependent energy shift of the relevant PL peaks revealed either type-I or type-II exciton formation depending on the strain distribution. This observation is in agreement with theoretical modeling. The present investigation shows that type-I band alignment—desired for electroluminescent devices—can be achieved by strain engineering.
Strain-Free Ge/Gesisn Quantum Cascade Lasers Based On L-Valley Intersubband Transitions, Greg Sun, H. H. Cheng, J. Menéndez, Jacob B. Khurgin, R. A. Soref
Strain-Free Ge/Gesisn Quantum Cascade Lasers Based On L-Valley Intersubband Transitions, Greg Sun, H. H. Cheng, J. Menéndez, Jacob B. Khurgin, R. A. Soref
Physics Faculty Publications
The authors propose a Ge/Ge0.76Si0.19Sn0.05 quantum cascade laser using intersubband transitions at L valleys of the conduction band which has a “clean” offset of150 meV situated below other energy valleys (Γ,X). The entire structure is strain-free because the lattice-matched Ge and Ge0.76Si0.19Sn0.05 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 the threshold current and potentially lead to room temperature operation.
Terahertz Gain In A Sige/Si Quantum Staircase Utilizing The Heavy-Hole Inverted Effective Mass, Richard A. Soref, Greg Sun
Terahertz Gain In A Sige/Si Quantum Staircase Utilizing The Heavy-Hole Inverted Effective Mass, Richard A. Soref, Greg Sun
Physics Faculty Publications
Modeling and design studies show that a strain-balanced Si1−xGex/Si superlattice onSi1−yGey-buffered Si can be engineered to give an inverted effective mass HH2 subband adjacent to HH1, thereby enabling a 77 K edge-emitting electrically pumped p–i–pquantum staircase laser for THz emission at energies below the 37 meV Ge–Ge optical phonon energy. Analysis of hole-phonon scattering, lifetimes, matrix elements, and hole populations indicates that a gain of 450 cm−1 will be feasible at f = 7.3 THz during 1.7 kA/cm2 current injection.
Sige/Si Thz Laser Based On Transitions Between Inverted Mass Light-Hole And Heavy-Hole Subbands, L. Friedman, Greg Sun, Richard A. Soref
Sige/Si Thz Laser Based On Transitions Between Inverted Mass Light-Hole And Heavy-Hole Subbands, L. Friedman, Greg Sun, Richard A. Soref
Physics Faculty Publications
We have investigated a SiGe/Si quantum-well laser based on transitions between the light-hole and heavy-hole subbands. The lasing occurs in the region of k space where the dispersion of ground-state light-hole subband is so nonparabolic that its effective mass is inverted. This kind of lasing mechanism makes total population inversion between the two subbands unnecessary. The laser structure can be electrically pumped through tunneling in a quantum cascade scheme. Optical gain as high as 172/cm at the wavelength of 50 μm can be achieved at the temperature of liquid nitrogen, even when the population of the upper laser subband is …