Grown on silicon: blue–violet InGaN laser diode operates at room-temperature

August 18, 2016 //By Julien Happich
Growing direct bandgap III-V semiconductor lasers directly on Si through heteroepitaxy, researchers at the Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO) in the Chinese Academy of Sciences (CAS) have managed to circumvent the defect-inducing material mismatches in lattice constant and Coefficient of Thermal Expansion (CTE).

In a paper recently published in Nature Photonics Letters titled "Room-temperature continuous-wave electrically injected InGaN-based laser directly grown on Si", they describe how a carefully engineered Al-composition step-graded AlN/AlGaN multilayer buffer between the Si and GaN successfully eliminated crack formation while also reducing the dislocation density.

Often, one way to circumvent the large lattice mismatch between GaN and Si (around 17%) is to integrate GaN laser diodes on silicon through heterogeneous chip-bonding, or designing the whole laser and driving circuitry on costly GaN wafers for later SiP integration. On monolithically integrated devices, because GaN shrinks twice as fast as Si when cooling down from the high process temperatures necessary for epitaxial growth (due to the difference in their CTE), defects and networks of micro-cracks propagate through the device, drastically lowering operation efficiency and yield.