Effects of Al grain size on metal-induced layer exchange growth of amorphous Ge thin film on glass substrate

Abstract

Metal-induced layer exchange (MILE) has attracted increasing attention as a way to lower the crystallization temperature of amorphous semiconductor thin films on insulating substrates. This paper demonstrates that the quality of the catalytic Al layer strongly influences the growth properties in the MILE of amorphous Ge. The growth velocity of the MILE significantly decreases with increasing the deposition temperature of Al (TAl: RT-200 °C), while the grain size of crystallized Ge becomes maximum (28 μm) at TAl = 100 °C. This behavior is attributed to the Al grain size depending on TAl, which influences both the nucleation frequency and the lateral growth velocity of Ge in Al. These findings give new insight into MILE for fabricating high-quality semiconductor thin films at low temperatures on inexpensive substrates.

Metal-induced layer exchange of group IV materials

“…These effects depend on the metal species, which reflects the deference of the screening effect, diffusion rate and interfacial energies [14,17,96]. The crystallization temperature can be also lowered (that is, LE can be facilitated) by: (i) controlling the semiconductor/metal interlayer [58,100,101], (ii) tuning the grain size of the metal layer [102][103][104], (iii) modulating the substrate surface condition [105], (iv) initial semiconductor doping in the metal layer [27,106,107], (v) applying eternal voltage during annealing [108] and (vi) introducing defects [109] or impurities [110][111][112] into the amorphous semiconductor layer.…”

“…Thin film preparation also contributes to large grain growth because the thinner metal layer requires greater lattice diffusion of semiconductor atoms in addition to grain boundary diffusion, which delays nucleation [96]. The metal grain size, that is the grain boundary density, affects the grain size of the resulting semiconductor layer because it changes the diffusion rate of the semiconductor atoms into the metal [102][103][104]. Higashi et al improved the lateral diffusion rate and induced large grain growth in the Ge-Au system by preparing a thin multilayer structure of Ge and Au (figure 7(d)) [99].…”

Low Energy Ion-Induced Crystallization of Ge in c-Al/a-Ge Bilayer Thin Films at Low Temperatures of ∼125 °C

“…The accumulation of Ge around Al grain boundaries due to enhanced diffusion leads to the nucleation and growth at the lowest ever temperature. , These are the main causes to reduce crystallization temperature. Table is prepared to show the interplay of various variables such as deposition methods, phase conversion conditions, and crystallization temperature in explaining a reduction in crystallization temperature. − ,,,,,− Better crystallization in Xe + ion-irradiated samples may also be understood in terms of recoils or the density of free atoms generated due to irradiation. It is evident that the number of recoils generated due to Xe + ions is significantly larger than that of Kr + ions.…”

“…Polycrystalline Ge ( poly -Ge) is an important material for its potential applications in low-cost semiconductor devices such as high density data storage devices, solar cells, flat panel displays, etc. − The performance of these devices can be significantly improved by reducing the fabrication temperature of poly -Ge near room temperature or at room temperature. The poly -Ge can be fabricated by different conventional process like solid phase crystallization (SPC), − laser crystallization, − and metal-induced crystallization (MIC). − Among these methods, the MIC process is an efficient, reliable, and well-known technique by which poly -Ge can be fabricated at relatively low temperatures (160–300 °C) from amorphous germanium ( a -Ge) film in the presence of certain transition metal (Al, Au, Cu, Ag, Ni, etc.) films, as compared to the SPC process in which a high annealing temperature of 375 °C is required for a long time. − In the past decade, post-transition metals such as Al (which constitutes a simple eutectic binary system with Ge and does not form any compound phases) has been extensively used to produce poly -Ge thin films, known as Al-induced crystallization (AIC). , This resulted in a sudden increase in the research activity aimed at reducing the crystallization temperature as well as decreasing the annealing time in aluminum-induced crystallization.…”

In Situ Optical Monitoring of New Pathways in the Metal-Induced Crystallization of Amorphous Ge

“…The main difference between standard (randomly oriented) AIC-Ge and oriented AIC-Ge is the presence of a carefully engineered diffusion barrier, usually an Al or Ge oxide (AlGeO x ), between the Al and Ge layers. Through various optimizations of layer thickness, temperature, diffusion barrier, substrate, and, more recently, Al-grain size, near complete(111)-oriented layers can be obtained. Additional work by Park et al on Au-induced crystallization of Ge shows that the chemical nature of the lower interface, Au-silica or Au-alumina, may promote Ge(100) orientation instead of (111).…”