51. Optimization of Graded Buffer Layers for Metamorphic Semiconductor Devices
- Author
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Minglei Cai, Tedi Kujofsa, Tanvirul Islam, Xinkang Chen, and John E. Ayers
- Subjects
010302 applied physics ,Materials science ,business.industry ,Metamorphic rock ,Transistor ,02 engineering and technology ,Semiconductor device ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Buffer (optical fiber) ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,Hardware and Architecture ,law ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,High electron ,Light-emitting diode ,Diode - Abstract
Metamorphic semiconductor devices such as high electron mobility transistors (HEMTs), light-emitting diodes (LEDs), laser diodes, and solar cells are grown on mismatched substrates and typically exhibit a high degree of lattice relaxation. In order to minimize the incorporation of threading defects it is common to use a linearly-graded buffer layer to accommodate the mismatch between the substrate and device layers. However, some work has suggested that buffer layers with non-linear grading could offer superior performance in terms of limiting the surface density of threading defects. In this work, we have compared S-graded buffer layers with different orders and thicknesses. To do so we calculated the expected surface threading dislocation density for each buffer design assuming a GaAs (001) substrate. The threading dislocation densities were calculated using the LMD model, in which the coefficient for second-order annihilation and coalescence reactions between threading dislocations is considered to be equal to the length of misfit dislocations.
- Published
- 2018