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Low temperature epitaxial deposition of GaN on LTCC substrates

Technological results about low temperature epitaxial deposition of GaN layers on LTCC substrates are reported. Epitaxial growths of GaN layers have been performed on commercially available LTCC substrates at 540 °C. Pre-growth preparations of the LTCC substrates has been carried out by aluminum oxide buffering layers on the LTCC surface. Further depositions have been performed in an epitaxial reactor using metal organic chemical vapor deposition (MOCVD) techniques with trimethylgallium (TMGa) and either RF or DC nitrogen plasma for different samples in a remote exposure configuration. The traditional precursor flow in MOCVD has been modified to separately introduce each precursor to the chamber, allowing increased lateral migration of adatoms and reduced vapour parasitics. The grown layers have been characterized by XRD, SEM, EDX, CTEM and HRTEM measurements. GaN (0002) XRD measurements show FWHM of 0.22° for peak position at 34.86° as the variations around these values for different samples are negligible. SEM measurements show uniform GaN layers with thicknesses around (520 ± 20) nm. EDX measurements have been used to verify the presence of gallium and nitrogen throughout the GaN structures and these results confirm GaN regions in the cross-sectional areas of the samples. Both CTEM and HRTEM measurements show well expressed crystal growth in direction that is normal to the LTCC surface. The CTEM, HRTEM and XRD results confirm crystallinity of the deposited GaN layers in direction normal to the surface. Based on the results, it can be concluded that the prepared GaN layers can be used as templates for further design of electronic devices based on this nitride semiconductor.