Temperature dependent optical properties of amorphous silicon for diode laser crystallization

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Amorphous silicon (a-Si) is a key material in various electronic and optical applications.
• Understanding its optical properties, particularly temperature dependence, is crucial for device performance and fabrication.
• Electron beam evaporation is a common method for depositing thin a-Si films.

Purpose of the Study:

• To determine the temperature-dependent optical parameters (refractive index n and extinction coefficient k) of electron beam evaporated amorphous silicon at 808 nm.
• To calculate the temperature and thickness-dependent absorption of a-Si layers.
• To assess the feasibility of diode laser crystallization for thin a-Si layers.

Main Methods:

• Optical characterization of amorphous silicon thin films using reflection measurements.
• Fitting an optical model to experimental reflection data to extract optical constants (n and k).
• Calculation of absorption coefficients based on determined optical parameters at varying temperatures.

Main Results:

• The temperature-dependent optical parameters n and k for amorphous silicon were determined at 808 nm.
• Absorption of a-Si layers increases significantly with temperature, by up to a factor of 4 at 600 °C compared to room temperature.
• Calculations show that this enhanced absorption allows for diode laser crystallization of a-Si layers as thin as 80 nm.

Conclusions:

• The optical absorption of amorphous silicon can be substantially enhanced by increasing temperature.
• Diode laser crystallization is a viable technique for fabricating thin amorphous silicon layers, facilitated by temperature-induced absorption increases.
• These findings are important for optimizing thin-film silicon device fabrication and processing.