Coupling of InGaN quantum-well photoluminescence to silver surface plasmons

The coincidence in excitation energy between surface plasmons on silver and the GaN band gap is exploited to couple the semiconductor spontaneous emission into the metal surface plasmons. A 3-nm InGaN/GaN quantum well (QW) is positioned 12 nm from an 8-nm silver layer, well within the surface plasmon fringing field depth. A spectrally sharp photoluminescence dip, by a factor \ensuremath{\approx}55, indicates that electron-hole energy is being rapidly transferred to plasmon excitation, due to the spatial overlap between the semiconductor QW and the surface plasmon electric field. Thus, spontaneous emission into surface plasmons is \ensuremath{\approx}55 times faster than normal spontaneous emission from InGaN quantum wells. If efficient antenna structures can be incorporated into the metal film, there could be a corresponding increase in external light emission efficiency.