Mikhail Belousov

Effect of Initial Bow of Sapphire Substrate on Substrate Curvature during InGaN Growth Stage of Light Emitting Diode Epitaxy

A systematic study to understand the relationship between wavelength uniformity and substrate curvature during InGaN growth is described in relation to the initial bow of sapphire substrate. The initial bow of the substrate acted as the offset parameter for its curvature throughout the stages of the epitaxy process. Substrate flatness during InGaN growth was found to be important for achieving high wavelength homogeneity. The impact of n-GaN layer thickness and InGaN growth temperature on the substrate curvature shape was investigated to obtain a perfectly flat substrate shape at the InGaN growth stage. Temperature adjustment showed a strong impact on substrate curvature at the InGaN growth stage. The best initial bow was found as a function of InGaN growth temperature, and the importance of the initial bow of the sapphire substrate for obtaining high homogeneity in light emitting diode (LED) wavelength was experimentally verified.

Application of Emissivity Compensated Pyrometry for Temperature Measurement and Control During Compound Semiconductors Manufacturing

Deposition processes for many Compound Semiconductors Devices (such as InGaAsP/InP infrared laser diodes or InGaP/GaAs heterojunction bipolar transistors) are extremely temperature sensitive with temperature windows as small as 2 °C to 3 °C. Requirements for process temperature repeatability can be less than ± 0.25 °C at temperatures in the range ∼ 650 °C to 750 °C which significantly exceed typical requirements for the silicon industry. While temperature control is a vital requirement for growing reproducible structures, wafer temperatures can deviate significantly from those measured by conventional techniques such as close proximity thermocouples or optical pyrometers. Elements (such as susceptor, wafer carrier and gaps filled by low pressure gas) located between the thermocouple and the wafer lead to measurement errors, particularly when the environment of the chamber changes such as during gas switching. Optical pyrometer measurements may have an error up to 100 °C due to emissivity oscillations duri...