Journal
JOURNAL OF APPLIED PHYSICS
Volume 107, Issue 1, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.3279307
Keywords
carrier density; conduction bands; effective mass; electronic density of states; elemental semiconductors; energy gap; germanium; k; p calculations; optical constants; tensile strength; valence bands
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Funding
- French Ministry of Industry under the Nano2012 convention
- RTRA Triangle de la Physique
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We have investigated the band structure of tensile-strained germanium using a 30 band k center dot p formalism. This multiband formalism allows to simultaneously describe the valence and conduction bands, including the L, Delta, and Gamma valleys. We calculate the energy band variation as a function of strain and obtain that the crossover from indirect to direct band gap occurs for a tensile in-plane strain of 1.9%. The effective masses of density of states are deduced from the calculated conduction and valence band density of states. Significant deviations are observed as compared to the effective masses of density of states values of unstrained bulk germanium. We finally calculate the optical gain that can be achieved with tensile-strained bulk germanium. An optical gain larger than 3000 cm(-1) is predicted for a carrier density of 1x10(18) cm(-3) and a 3% in-plane biaxial strain. This optical gain is larger than the one of GaAs calculated with the same formalism and is much larger than the experimental free-carrier absorption losses. This gain should be sufficient to achieve lasing in these structures.
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