Research And Implementation Of Surface Temperature Monitoring During The Gallium Nitride Epitaxial Growth

Gallium nitride is the group Ⅲ/Ⅴ direct bandgap semiconductor crystal, which has played a great role in promoting research and development in the field of blue and violet light emitting device. It’s the third generation semiconductor material after the first generation material, Silicon and the second generation material GaAs, InP, which has broad prospects in optoelectronics, high-frequency microwave devices and high-power device applications. Metal Organic Chemical Vapor Deposition(MOCVD) method is the newest generation of compound semiconductor device manufacturing technology, MOCVD equipment are widely used in industry because of their excellent quality and high production capacity. But surface temperature measurement during GaN MOCVD is particularly difficult because the epilayers and substrates(typically sapphire) are transparent at the near-IR wavelengths normally used for pyrometry. In this paper we describe a method and ancillary equipment for monitoring the true surface temperature of the gallium nitride during it’s epitaxial growth. Thesis mainly investigated contents are as follows:(a) Analysis the different temperature measurement ways and find one solution is to detect radiation near 400 nm(UVviolet range, or UVV) where the GaN epilayers are opaque at the high temperatures encountered during deposition. Analysis the weak signal detection solutions and find ways to get rid of background noise according the feature of signal and noise.(b) Design on-line monitoring system testing and fixing method according to the structure of MOCVD device. Save space for another on-line monitoring equipment installation by designing optical and mechanical structure into normal incidence type. Large field of view and anti-vibration design of the optical path of the probe make sure the probe inclined at an angle within the range of 1°, the reflected signal intensity changes within 2%.(c) Achieve a photomultiplier tube amplification control and constant power control of LED light source, use one photomultiplier tube measuring thermal radiation and reflectivity and through the control of software to control the LED indensity to keep the same emitting indensity magnitude with thermal radiation..Through analysis the experiments and field test data with the temperature monitoring system, the temperature monitoring system temperature measurement range is 750 ~ 1200℃, repeatability within 1℃; Temperature measurement uncertainty is 3℃ during the range of 750 ~ 870℃; The temperature measurement accuracy within 1℃, temperature measurement uncertainty is 0.5℃ in the range of 870 ~ 1200℃. Wherein when more than 1000℃, temperature measurement uncertainty less than 0.2℃.。The temperature monitor system developed in this paper realized true surface temperature measurement and which has been verified in Prismo D-Blue? 485 MOCVD machine platform that is self-developed by AMEC.