Growth of high quality Ge-on-Si layer by using an ultra-thin LT-Si buffer in RPCVD

摘要

Ge epitaxial layer on Si substrate becomes more attractive for Si-based monolithic photonic integrated circuit(PIC).Low threading dislocation density and low surface roughness play a vital role in realizing the fabrication of the Ge optoelectronic devices.In this study,an ultra-thin LT-Si buffer for the deposition of Ge layer was investigated with regard to Ge layer's crystallinity,symmetrical characteristic,threading dislocation density,and surface roughness.As a result,Ge epitaxial film has low threading dislocation density(TDD=5×106cm~(-2))and smooth surface(RMS= 0.68nm)in 5μmx5μm scan field with the Ge epitaxial layer thickness of about 1μm.What's more,it was grown in a short time by using an ultra-thin LT-Si buffer layer without using chemical mechanical polishing(CMP),high temperature annealing,H2 annealing or cyclic annealing.In addition,room temperature direct gap photo luminescence was observed from intrinsic tensile-strained(0.21%)Ge-on-Si layer and bandgap narrowing in Ge epitaxial layer is 85meV.