GalnN Quantum Wells Microstructure

The most common way of fabricating GalnN/GaN heterostructures is by means of heteroepitaxy of GaN and GalnN on sapphire or SiC substrates. In fact, this leads to wurtzite GaN, which is now the commonly used modification. Even though there is considerable effort being devoted to producing cubic GaN structures, we will restrict our discussion to the hexagonal phase, since practically all the work on heterostructures concentrates on the wurtzite structure. [Pg.514]

GalnN quantum wells (QWs) sandwiched between GaN layers grown on sapphire or SiC are expected to be subject to these fundamental defects, too. Moreover, due to the rather large lattice mismatch between GaN and InN, the GalnN layer itself may contain new defects, when the critical thickness is exceeded. In addition, GaN and InN may be subject to a partial immiscibility and phase separation, which also produces defect structures. [Pg.514]

It is now being widely discussed whether phase separation of GalnN into InN mid GaN due to their large differences in lattice constants plays a decisive role for the properties of GalnN/GaN quantum wells. Its influence on the optical properties and on lasing from such quantum wells is discussed in Datareview C2.5. [Pg.514]

Phase separation and immiscibility is a well-known phenomenon for almost all solid solutions [3], It arises from a lower free energy of the separated components due to a large strain in the mixed crystal. It is therefore expected to occur primarily under close-to-equilibrium growth conditions. [Pg.514]

Phase separation has been studied in great detail, e.g. in the GalnAsP material system, where a large miscibility gap was found both experimentally and theoretically [3], On a microscopic scale, large compositional variations were observed by dark-field transmission electron microscopy, with length scales of the order 10-20 nm. [Pg.514]

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