Preparation of Poly-Ge Considering its Application to a-Si/Poly-Ge Multilayer Structures by a Low-Temperature Solid Phase Crystallization Method

Poly-Ge films with good crystallinity were prepared by a low-temperature solid phase crystallization (SPC) method for application to multilayer a-Si/poly-Ge structures. Using a-Ge:H films prepared at just below the thermal decomposition temperature of GeH4 gas as the starting material for SPC, high-quality poly-Ge with Ge<111> peak orientation was obtained after low-temperature annealing at 350°C for 2 h in a nitrogen atmosphere. Furthermore, the selective crystallization of a-Ge:H sublayers in an a-Si:H( ∼50 Å)/a-Ge:H( ∼1000 Å) multilayer film was achieved by annealing at 350°C. The poly-Ge sublayers included large crystal grains with dimensions of about 3000 Å, which were three times as thick as the poly-Ge sublayers.