Comparison of Chirped Superlattices and Linearly-Graded Buffer Layers As Adjustable-Strain Platforms for Metamorphic InAaAs/GaAs (001) Devices

Abstract

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.