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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2016. V. 1, N 1. P. 001-008.
Lowering the density of dislocations in heteroepitaxial
III-nitride layers: Effect of sapphire substrate treatment (review)
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, propect Nauki, 03028 Kyiv, Ukraine
E-mail: anatoliy.evtukh@gmail.com
Abstract. In this paper, different methods for lowering the dislocation density such as incorporation of the buffer layers, substrate patterning and nitridation, silan-ammonia treatment are reviewed and compared. Advantages and limitations of these methods as well as a specific mechanism to reduce the dislocation amount are discussed. Usually, high densities of threading dislocations within the range 1010…1011 cm–2 are present in typical thin nitride films that are directly grown on sapphire substrate. Using these methods for substrate preparation, the density of dislocations can be reduced to the value 1∙107 cm–2. An important process that enables to obtain the high-quality GaN layers with the low dislocation density is patterning the sapphire substrate. The dislocation density of these substrates depends on the pattern shape and orientation of patterned strips on c-plane sapphire. Layers of GaN grown on a cone-shaped pattern have the lowest dislocation density. In addition, patterning the sapphire substrate increases the external quantum efficiency of radiative structures and reduces the mechanical stresses in the nitride layers. Keywords: GaN layer, sapphire substrate, density of dislocations, reduction, patterning, treatment.
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