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 technique 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 investigate the impact of temperature on the absorption coefficient of a-Si layers.
• To assess the feasibility of diode laser crystallization for thin a-Si films.

Main Methods:

• Optical modeling was employed to fit the layer system's reflection values.
• A femtosecond (fs) laser beam was used to probe the optical response.
• Temperature-dependent measurements were conducted up to 600 °C.

Main Results:

• The temperature-dependent optical parameters n(T) and k(T) for amorphous silicon were successfully determined at 808 nm.
• Calculations revealed that absorption in a-Si layers increases significantly with temperature at this wavelength.
• Absorption was found to increase by a factor of 4 when heating layers to 600 °C compared to room temperature.

Conclusions:

• The significant increase in absorption with temperature allows for efficient diode laser crystallization.
• Thin amorphous silicon layers, as thin as 80 nm, can be crystallized using diode laser techniques.
• This temperature-dependent optical behavior offers a pathway for advanced fabrication of amorphous silicon-based devices.