Fabrication and Quantum Confinement Investigation of Ge Multiple Quantum Wells with Si3N4 Barriers

Abstract

Fabrication process and quantum confinement effect of Ge multiple quantum wells (MQWs) structure with Si3N4 barriers were investigated for its potential application in 3rd-Generation tandem solar cells. The structure was fabricated by alternating deposition of Ge and Si3N4 layers using magnetron co-sputtering and crystallized by rapid thermal annealing (RTA). The Ge MQWs structures were characterized by X-ray reflection, Raman microscopy and glancing incidence X-ray diffraction. Optical properties were analyzed by transmission and reflection measurements. Above characterizations demonstrated that Ge has formed polycrystalline layers restrained between amorphous Si3N4 barriers after annealing. The crystallization temperature increased with decreasing Ge layer thickness; in other words, thicker Ge layer is prone to crystallize. And this Ge layer crystallinity is found to be important in deciding quantum confinement effect achieved in the multilayer structure.