The nitride semiconductors (AlN, GaN, InN) are subject to a large research effort due to their numerous applications, such as light emitting diodes, high power and high frequency components. The aim of this work has been twofold: to investigate the electrical conduction in InN layers and the origin of the high emission efficiency in InGaN/GaN Quantum Wells (QWs). The surface electron accumulation in InN layers is still an important limitation to device applications. We have explored this point using low frequency noise measurements on Plasma Assisted Molecular Beam Epitaxy (PAMBE) InN layers and we demonstrated that the bulk electrical conductivity of InN can be accessed. The investigation of quantum wells produced by Molecular Beam Epitaxy (MBE) or Metalorganic Vapour Phase Epitaxy (MOVPE), has been carried out through microstructural analyses by Transmission Electron Microscopy techniques(TEM, HRTEM, STEM) in correlation with optical properties on a large number of samples grown in different growth conditions. This experimental work has allowed us to obtain a critical view on the role of the growth conditions and such parameters as the well morphology, composition fluctuations, as well as the V shaped defects on the current explanations of high emission efficiency in InGaN/GaN QWs.
Structural, optical and electronic properties of InN films and In rich heterostructures for optoelectronic applications