Chirped Superlattices as Adjustable Strain Platforms for Metamorphic Semiconductor Devices

Tuesday, 3 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
X. Chen, M. T. Islam, T. Kujofsa, and J. E. Ayers (University of Connecticut)
Chirped superlattices are of interest as buffer layers in metamorphic semiconductor device structures, because they can combine the mismatch accommodating properties of compositionally-graded layers with the dislocation filtering properties of superlattices. Important practical aspects of the chirped superlattice as a buffer layer are the surface strain and surface in-plane lattice constant. In this work we study two basic types of InGaAs/GaAs chirped superlattice buffers; type I is compositionally modulated while type II is thickness modulated. For both types, we have studied the equilibrium surface strain and surface in-plane lattice constant, and we have compared the surface strain behavior to linearly-graded buffers having the same top target composition of indium.