Speaker
Description
In the last decade, several activities have shown how the performance of Ge-based optoelectronic devices, often required to operate in a wide temperature range, critically depends on both their strain status and on the carrier population of nearly degenerate bands, which are non-trivial function of the temperature. In this work, we provide a systematic study on how the temperature dependent distribution of strain can impact the optical performance of semiconductor devices. To this aim, we have investigated strained Ge microstructures, considering the influence of mechanical and thermo-mechanical features on the optical properties, instrumental to develop a thorough guideline in the assessment and design of integrated light emitters. In particular, we consider Ge micropillars with Silicon nitride (SiN) stressor layer deposited on top. The mechanical deformation is described by means of 3D finite element calculations, evidencing the impact of the lattice temperature on the lattice distortion induced by the SiN stressor material. To this aim we include the surface and longitudinal strain variations, together with off-diagonal strain components. The numerical data describing the stressor-induced surface strain is compared with experimental results, obtained by means of µ-Raman spectroscopy. A theoretical multi-valley effective mass method, including also the contribution of thermal strain and the effect of the strain gradient, is shown to fully capture the experimental photoluminescence spectroscopy experiments (PL), giving a strong theoretical insight into the interpretation of the spectra lineshape which results to be influenced by the non-uniform strain field. The combination of theoretical and experimental results allowed us to disentagle thermo-mechanical effects from those related to a temperature induced variation of the carrier distribution, a critical aspect for optoelectronic devices operating in a wide temperature range. In perspective, our comprehensive approach can be applied to the design and characterization of strain-based electronic and opto-electronic devices, providing a quantitative description of the temperature-dependent strain relaxation mechanism thus elucidating how heating can impact the optical performance.
| Category | Solid State (Experiment) |
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