GaN on Si(111): From growth optimization to optical properties of quantum well structures

In this paper, we report on the growth of GaN films and AlGaN/GaN multiple quantum wells (MQWs) on Si(111) substrates by molecular beam epitaxy using ammonia as nitrogen source. A smooth layer-by-layer two-dimensional growth mode allows to obtain reflection high-energy electron diffraction intensity oscillations during GaN, AlN and AlGaN growth. Low temperature photolumine scence (PL) spectra of thick nearly relaxed GaN films are dominated by an i ntense excitonic emission at 3.471 eV having a full width at half maximum o f 5 meV. On the other hand, the PL spectra of thick strained GaN films exhi bit a broad band edge emission at 3.455 eV having a full width at half maxi mum of 15 meV. As revealed by transmission electron microscopy, AlGaN/GaN M QW structures with sharp interfaces are achieved on Si(lll) substrates and each QW exhibits a clearly resolved PL emission peak.