Low-Temperature Formation of Large-Grain (≥10 μm) Ge at Controlled-Position on Insulator by Gold-Induced Crystallization Combined with Diffusion-Barrier Patterning

Abstract

Formation of position-controlled large-grain (≥10 μm) Ge crystals on insulator is realized at low-temperature (300 • C) by goldinduced-crystallization using a-Ge/Au stacked structures. By introduction of diffusion barriers, i.e., thin-Al 2 O 3 layers (2 nm thickness), having open-windows (3-20 μm diameter) into the a-Ge/Au interfaces, Ge crystals are selectively grown from the open windows. For open-windows with diameter of 20 μm, the grown areas consist of several Ge (111) grains. This is attributed to that several nuclei acting as seed are generated around the perimeters of the open windows. The number of seeds is linearly decreased by decreasing of the open-window diameter. As a result, (111)-oriented large (∼10 μm) Ge single-crystals, without any grain boundary, are obtained at controlled positions for open-windows with diameter of 3 μm. This technique will facilitate realization of flexible electronics and 3-dimensional large-scale integrated circuits, where Ge-based functional high-performance thin-film devices are integrated on flexible plastic substrates and/or amorphous insulating layers.

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

“…After 10 days of annealing at 300°C, Al regions were interconnected with each other; in other words, layer exchange occurred. Furthermore, there are many studies where the annealing time is too long for Au‐induced layer exchange crystallization . In this study, Au‐rich regions were not interconnected with each other so no layer exchange was observed.…”

“…Separation of the electrodes was kept 0.5 mm, and electrode length was 5 mm. Prior to electrical characterization of Ge films, Au clusters on the Ge layers were etched away by using a solution containing KI (20 g) and I 2 (5 g) per 100‐mL H 2 O . The electrical properties were performed by Keithley 2440 source‐meter for I‐V analysis under no illumination.…”

(Invited) Low-Temperature Growth of Orientation-Controlled Large-Grain Ge-Rich SiGe on Insulator at Controlled-Position for Flexible Electronics

“…This will enable position-control of crystals. To examine this, we investigate the GIC process combined with diffusion control layer patterning (36).…”

Crystallization of Ge thin films by Au-induced layer exchange: effect of Au layer thickness on Ge crystal orientation

“…This temperature is low enough to use plastic films such as polyimide for substrates and many advances have been reported for this system. [22][23][24][25][26][27][28][29][30][31][32][33] In a recent work, 26) a multilayer structure of Au and amorphous Ge (a-Ge) with a very thin Au layer of 0.5 nm has been employed to promote the reaction between Au and a-Ge layers. This result implies that Au layer thickness has an important effect on crystallization behavior.…”