III-Nitride growth on silicon (GaN/Si)
When substrates and epi-layers have a large lattice mismatch and a large mismatch of thermal expansion coefficient, a high dislocation density and high tensile stress cause critical wafer bowing and, finally, cracking. Therefore, complex devices such as GaN-based structures on silicon require precise strain engineering to achieve a high quality material. LayTec’s in-situ metrology systems provide direct monitoring of the critical growth parameters for stress compensation and strain engineering. Our tools are used world-wide to improve the performance of power electronic devices (e.g. FET) and optoelectronics (e.g. LEDs).
In-situ tool EpiCurve® TT helps to meet challenges of GaN growth on Si(111) and to prevent cracking. For example, at the Institue of Material and Research Engineering (IMRE, A*STAR) in Singapore, EpiCurve®Triple TT is used in the development of epiwafers for InGaN/GaN LEDs and GaN power electronic devices. The tool is ideally suited for GaN growth optimization on 200 mm silicon because its 3 sensor heads provide radial analysis of growth conditions. In comparison to the time consuming, destructive ex-situ cross section transmission electron microscopy (TEM) analysis, the in-situ tool provides real-time information on growth thickness, wafer bow, temperature and growth homogeneity already during growth.
According to the researchers at IMRE, EpiCurve®Triple TT has significantly reduced R&D cycles for epitaxial growth optimization and enables faster industrialization of GaN/Si technology. Please find further details about in-situ measurements at IMRE including reflectance screenshots in our newsletter
The experience of GaN growth on Si(111) is now transferred to growth on Si(001) and Si(110), because GaN based power electronics can be easily integrated with Si standard electronics (CMOS) and is available in large sizes up to 300 mm. Our research partner Otto-von-Guericke University in Magdeburg, Germany develops high performance GaN HEMT structures on Si(001) with highly optimized interlayers for stress and defect density control. The researchers use LayTec's EpiCurve® TT in their strain engineering to monitor wafer curvature, growth rates and the structural interface quality. This information helps adjust growth parameters and improve the quality of GaN/Si. For further details including screenshots please download our newsletter
In-situ benefits for GaN/Si growth
LayTec's EpiCurve® TT system monitors such critical parameters as wafer bowing (including asphericity measurements), temperature homogeneity and layer thickness, which have direct impact on the crystalline quality, ternary composition and, therefore, the final device quality. EpiCurve's asphericity signal can be used as early warning for subsequent occurence of plastic deformations. Furthermore, the measured curvature and temperature data directly correlate with the final photoluminescence (PL) homogeneity of optoelectronic devices. For further details please ask us for the talk presented at the 10th International Conference on Nitride Semiconductors (ICNS-X) by sending your request to email@example.com.