Buried tunnel junction current injection for InP-based nanomembrane photonic crystal surface emitting lasers on Silicon

Silicon-integrated laser sources are of great interest for chip-level optical interconnects and significant efforts have been devoted to their development during recent years, with the most promising approaches being due to heterogeneous integration of III-V semiconductor based active material on silicon substrate. We have previously demonstrated optically pumped ultra-compact InP-based surface-emitting membrane lasers on silicon using transfer print technology. For electrically pumped devices, a uniform and efficient current injection in ultrathin device structures with laterally displaced electrodes is inherently difficult to achieve. The current feeding and spreading layers are heavily restricted in thickness which by traditional methods would lead to uneven carrier injection, enhanced optical absorption and excessive Joule heating, in the end compromising the device performance. Here we investigate a buried tunnel junction (BTJ) current injection scheme using selective etching and epitaxial regrowth for lateral confinement. In this approach the current injection layers are almost exclusively n-type which leads to reduced optical absorption and increased electrical conductivity, and the TJ heterostructure ensures an even injection profile also for large-area devices. Membrane-type BTJ light-emitting diodes and photonic crystal surface emitting laser structures are demonstrated with low series resistance, efficient carrier confinement and laterally uniform current injection over large area.