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

Abstract

Gold-induced (Au-) crystallization of amorphous germanium (α-Ge) thin films was investigated by depositing Ge on aluminum-doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X-ray diffraction, and scanning electron microscopy. The Raman and X-ray diffraction results indicated that the Au-induced crystallization of the Ge films yielded crystallization at temperature as low as 300°Cfor 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current-voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm −1 for annealed samples grown on aluminum-doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge-based electronic and photovoltaic applications.

State of the art of ultra-thin gold layers: formation fundamentals and applications

“…Besides the applications for optical properties and electronic devices, UTGLs were also reported to act as the seed layer for the growth of other thin lms. [116][117][118][119][120][121][122][123][124][125] Regarding the Au-induced thin lm growth, using UTGLs to facilitate the formation of crystalline germanium (c-Ge) thin lms is among the examples which attracted interests in recent years. [116][117][118][120][121][122] N. Sunthornpan et al investigated how the thickness of the Au seed layer affected the low-temperature crystallization process of Ge thin lms.…”

“…[116][117][118][119][120][121][122][123][124][125] Regarding the Au-induced thin lm growth, using UTGLs to facilitate the formation of crystalline germanium (c-Ge) thin lms is among the examples which attracted interests in recent years. [116][117][118][120][121][122] N. Sunthornpan et al investigated how the thickness of the Au seed layer affected the low-temperature crystallization process of Ge thin lms. 122 Au layers with variable thicknesses of 1 nm, 2.5 nm, 5 nm, 7.5 nm, and 10 nm were rst sputter-deposited on the Si substrates, followed by the amorphous Ge thin lms (30 nm) deposition also by the sputter deposition.…”

“…In recent years, more and more applications based on UTGL configurations have been reported, including the examples from optical applications, 6,7,96–106 electronic device applications, 107–115 and as seed layers. 116–125…”

Laser Crystallization of Amorphous Ge Thin Films via a Nanosecond Pulsed Infrared Laser

“…2−10 In a similar manner to Si, high-quality crystallization of substrate-deposited amorphous Ge (a-Ge) films has attracted interest for its uses as an IR-sensitive material due to its lower band gap. Different techniques have been applied to produce polycrystalline Ge (pc-Ge) films, such as solid phase crystallization (SPC), 11 metal-induced crystallization (MIC), 12,13 and laser annealing. 14−17 However, crystallization of a-Ge with the SPC process requires a high annealing temperature of around 500 °C, which is not applicable for every type of substrate.…”

“…Amorphous silicon (a-Si) films have been extensively studied using thermal and light-based crystallization for application in solar cells in order to benefit from the low cost of film deposition versus the high cost of crystal growth while maintaining the crystalline quality of the active material. − In a similar manner to Si, high-quality crystallization of substrate-deposited amorphous Ge (a-Ge) films has attracted interest for its uses as an IR-sensitive material due to its lower band gap. Different techniques have been applied to produce polycrystalline Ge (pc-Ge) films, such as solid phase crystallization (SPC), metal-induced crystallization (MIC), , and laser annealing. − However, crystallization of a-Ge with the SPC process requires a high annealing temperature of around 500 °C, which is not applicable for every type of substrate. MIC has low-temperature processing; however, the employed semiconductor properties are deteriorated due to metal contamination.…”