Stimulated emission at 288 nm from silicon-doped AlGaN-based multiple-quantum-well laser.

We demonstrated stimulated emission at 288 nm from a silicon-doped AlGaN-based multiple-quantum-well (MQW) ultraviolet (UV) laser grown on sapphire. The optical pumping threshold energy density of the UV laser was 64 mJ/cm2, while lasing behavior was not observed in undoped AlGaN MQWs. This means silicon doping could effectively reduce the lasing threshold of UV lasers, and the mechanism was studied showing that the silicon-doped AlGaN MQWs had a 41% higher internal quantum efficiency (IQE) compared with the undoped one. The transmission electron microscopy characterization showed that silicon doping explicitly improved the crystallographic quality of MQWs. Calculation of the polarization charge in the MQWs further revealed that the advantage of better structure quality outweighed the reduction of internal polarization field by Si doping for the IQE enhancement and successful stimulated emission.