Growth promotion of Al-induced crystallized Ge films on insulators by insertion of a Ge membrane below the Al layer

Abstract

Al-induced crystallization (AIC) enables low-temperature crystallization of amorphous Ge thin films on insulators. We investigated growth promotion of Ge thin films using Ge membranes (1–10nm thickness) that are initially inserted below the Al layer. These Ge insertion layers enhanced supersaturation of Al with Ge, which results in low-temperature AIC (275°C). However, thick (≥3nm) insertion layers result in small grains because of the high nucleation frequency. A 1-nm-thick insertion layer accomplished a growth promotion and yielded large grains of over 100μm in diameter. Moreover, electron backscatter diffraction measurement revealed that the AIC-Ge layer was highly (111) oriented. This low-temperature crystallization technique opens up the possibility for developing Ge-based electronic devices on inexpensive glass substrates, as well as on flexible polymer substrates.