Finite Element Stress Model of Direct Band Gap Ge Implementation Method Compatible with Si Process

Abstract

As an indirect band gap semiconductor, germanium (Ge) can be transformed into a direct band gap semiconductor through some specific modified methods, stress, and alloying effect. Direct band gap-modified Ge semiconductors with a high carrier mobility and radiation recombination efficiency can be applied to optoelectronic devices, which can improve the luminous efficiency dramatically, and they also have the potential application advantages in realizing monolithic optoelectronic integration (MOEI) and become a research hotspot in material fields. Among the various implementations of Ge band gap-type conversion, the related methods that are compatible with the Si process are most promising. It is such a method to etch around the Ge epitaxial layer on the Si substrate and introduce the biaxial tensile stress by SiGe selective filling. However, the influence of the width of the epitaxial layer, Ge composition, and Ge mesa region width on strain distribution and intensity is not clear yet. Accordingly, a finite element stress model of the selective epitaxy-induced direct band gap Ge scheme is established to obtain the material physical and geometric parameters of the Si _{1− x} Ge _x growth region. The result of finite element simulation indicates when the Si _{1− x} Ge _x epitaxial layer is 150–250 nm wide and the Ge composition is 0.3∼0.5, Ge mesa with 20–40 nm in width can be transformed into direct band gap semiconductors in the depth of 0–6 nm. The theoretical results can provide an important theoretical basis for the realization of subsequent related processes.