Group III Nitrides offer the possibility to elaborate laser diodes (LDs) and high brightness light emitting diodes (LEDs) that can range from ultraviolet to blue (400 to 490 nm) due to their active zone which is composed of InGaN/GaN quantum wells (QWs). The green range is missing in the color palette of LDs and high brightness LEDs. It is due to both the difficulty to increase the In content above 20-25% (low miscibility of In in GaN and difference in lattice parameter) and to the degradation of high In content QWs at high growth temperature (above 750°C). Metalorganic vapour phase epitaxy (MOVPE) is the proof growth technique which guaranties high efficiency blue LEDs. However, for high In content QWs, the p-type GaN layer, which is grown on top of the active zone at 1000°C, degrades significantly the device efficiency. Although LEDs grown by molecular beam epitaxy (MBE) have still not demonstrated high efficiency InGaN/GaN QWs, this technique offers the possibility to grow p-type GaN at low temperature (740°C) and would thus be of interest for the elaboration of high brightness green LEDs. However, understanding the low radiative efficiency of InGaN/GaN QWs grown by this technique is still a challenge. Different works, such as those of Hangleiter et al., Chichibu et al., or Sonderegger et al., have proposed different possible explanations accounting for the high efficiency of MOCVD QWs. In this work, we propose to study the quantum efficiency discrepancies of InGaN/GaN QWs grown by both MBE and MOVPE techniques. Two InGaN/GaN QWs with 25% In content but with different well width (1,5nm and 2,5nm) were prepared. The four samples are analyzed by photoluminescence (PL), micro-photoluminescence, atomic force microscopy and cathodoluminescence. Comparing the PL intensity for different excitation wavelength and as a function of the temperature allows us to extract the internal quantum efficiency.

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1. Room temperature polariton lasing and condensation effects in III-nitride microcavities
2. Control of the polarity and crystal face of GaN epilayers grown by MBE