Dislocation-Based Thermodynamic Models of V-Pits Formation and Strain Relaxation in InGaN/GaN Epilayers on Si Substrates
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The strain relaxation mechanism in III-N materials is occurred through the motion of dislocations that generated at III-N/Si interface as a result of large mismatch in lattice and thermal expansion coefficients. As a result of the large lattice mismatch between different layers, the upper layer gets strained and with thicker layers, the strain energy increases until a thickness limit called the critical material thickness. Most of such dislocations (threading dislocations) penetrate the top surface forming V-pits defects at the top surface that relax the material. These V-pits directly affect the device efficiency, performance, and reliability. Therefore, in this paper, a thermodynamics-based model will be used to study the V-pits formulation and growth in the III-N (especially, InGaN-based materials). In this model, three types of energies are used under a balanced system to model the V-pit formation and growth. These energies are the strain energy in the InGaN epilayer, the destruction energy as a result of dislocation to form the V-pit, and the strain energy of the V-pits facets that generated during the facet nucleation.
KeywordsThreading dislocations III-Nitride relaxation V-pits defects Thermodynamics modeling
The support from the Young Investigators Research Grant (No. YIRG05) at the British University in Egypt and Research Grant from the Academy of Scientific Research and Technology (ASRT) are greatly appreciated.
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