A group-IV double heterostructure light emitting diode for room temperature gain in Silicon

The lack of straightforward epitaxial integration of useful telecom lasers on silicon remains the major bottleneck for bringing optical interconnect technology down to the on-chip level. Crystalline silicon itself, an indirect semiconductor, is a poor light emitter. Here, we identify conceptionally simple Si/Si$_{1-x}$Ge$_x$/Si double heterostructures (DHS) with large Ge content ($x \gtrsim 0.4$) as auspicious gain material suitable for Si-based integrated optics. In particular, using self-consistent Poisson-current transport calculations, we show that Si diodes containing a 16 nm thick Si$_{1-x}$Ge$_x$ layer of high crystalline quality, centered at the p-n junction, results in efficient carrier accumulation in the DHS and gain if the diode is driven in forward direction. Despite the high strain, we unambiguously demonstrate that such prior unattainable defect-free DHS can be fabricated using ultra-low temperature epitaxy at pristine growth pressures. Telecom light emission is persistent up to 360 K, and directly linked to a ~160 meV high conduction band barrier for minority electron injection. This epitaxy approach allows further increasing the Ge content in the DHS and creating dot-in-well heterostructures for which even higher gains are predicted. Thus, the surprisingly facile DHS presented here can be an essential step toward novel classes of group-IV optoelectronic devices for silicon photonics.