Publication details
Light emission from direct band gap germanium containing split-interstitial defects
| Authors | |
|---|---|
| Year of publication | 2021 |
| Type | Article in Periodical |
| Magazine / Source | Physical Review B |
| MU Faculty or unit | |
| Citation | |
| Web | https://doi.org/10.1103/PhysRevB.103.085310 |
| Doi | http://dx.doi.org/10.1103/PhysRevB.103.085310 |
| Keywords | Spontaneous emission; k dot p method; Electronic structure; first-principles calculations; interstitials |
| Description | The lack of useful and cost-efficient group-IV direct band gap light emitters still presents the main bottle-neck for complementary metal-oxide semiconductor-compatible short-distance data transmission, single-photon emission, and sensing based on silicon photonics. Germanium, a group-IV element like Si, is already widely used in silicon fabs. While the energy band gap of Ge is intrinsically indirect, we predict that the insertion of Ge-Ge split-[110] interstitials into crystalline Ge can open up a direct band gap transmission path. Here, we calculate from first principles the band structure and optical emission properties of Ge, Sb, and Sn split-[110] interstitials in bulk and low-dimensional Ge at different doping concentrations. Two types of electronic states provide the light-emission enhancement below the direct band gap of Ge: a hybridized L-Gamma state at the Brillouin zone center and a conduction band of Delta band character that couples to a raised valence band along the Gamma-X direction. Majority carrier introduced to the system through doping can enhance light emission by saturation of nonradiative paths. Ge-Sn split interstitials in Ge shift the top of the valence band towards the Gamma-X direction and increase the Gamma character of the L-Gamma state, which results in a shift to longer emission wavelengths. Key spectral regions for datacom and sensing applications can be covered by applying quantum confinement in defect-enhanced Ge quantum dots for an emission wavelength shift from the midinfrared to the telecom regime. |