Nanometer-thin ALD-Al₂O₃for the improvement of the structural quality of AlN grown on sapphire substrate by MOVPE

Abstract

The epitaxial quality of AlN grown on sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) is improved upon the incorporation of nanometer‐thin amorphous Al2O3 interlayer by atomic layer deposition (ALD). The critical ALD‐Al2O3 thickness is determined to be around 1 nm, where the AlN exhibits a parallel step‐and‐terrace surface morphology. However, with increasing ALD‐Al2O3 thickness, the surface changes to meandering step‐and‐terrace morphology due to the formation of surface defects in the ALD‐Al2O3, leading to growth spiral in AlN. The surface defects are attributed to the transformation of amorphous Al2O3 into crystalline structure. The same tendency in the structural quality is also observed by XRD measurements, where the ω‐scan of symmetric (0002) and asymmetric (10true1¯2) reflections increases with ALD‐Al2O3 thickness. Raman analysis and XRD measurements both confirm that AlN epilayers exhibit tensile strain and approach the relaxed state with increasing ALD‐Al2O3 thickness. The high‐quality AlN grown on 1‐nm‐thin ALD‐Al2O3 exhibits the highest tensile strain, effectively circumventing the relaxation through the reduction of threading dislocations.

Effect of Boron Incorporation on Structural and Optical Properties of AlN Layers Grown by Metal‐Organic Vapor Phase Epitaxy

“…The AlN and B‐doped AlN layers were grown under low‐pressure (1.3 × 10 3 Pa) and high‐temperature (1280 °C) conditions . Details of the growth conditions for the AlN layers were reported elsewhere . Typical B‐doping effects on the growth rate and structural quality of AlN layers are presented in Appendix A.…”

“…[22,23,27,28] Details of the growth conditions for the AlN layers were reported elsewhere. [29,30] cannot be evaluated by O þ secondary ions with the same mass; e.g., 16 O þ secondary ions cause the easy saturation of the detection signal and 18 O þ secondary ions lead to poor resolution of [O]. Therefore, 16 þ primary ions were used in an alternately pulsed mode with an accelerating voltage of 15 and 2 kV, respectively.…”

Effect of Sputter Deposition Atmosphere of AlN on the Electrical Properties of Hydrogen‐Terminated Diamond Field Effect Transistor with AlN/Al2O3 Stack Gate

“…Next, to protect the hole conductive layer of H‐diamond surface, the 5‐nm‐thin amorphous ALD‐Al 2 O 3 was deposited at 120 °C. The detailed growth and deposition conditions of diamond and ALD‐Al 2 O 3 are already described . On the other hand, the SD‐AlN(Ar+N 2 ) was deposited on ALD‐Al 2 O 3 at room temperature.…”

Residual stress analysis of aluminum nitride piezoelectric micromachined ultrasonic transducers using Raman spectroscopy

“…Other techniques that have been used to measure residual stress in AlN thin films include the ion beam layer removal (ILR) method, 34 bulge testing, 35 x-ray diffraction (XRD), 2,29,36,37 Fourier transform infrared spectroscopy (FTIR), 29,38,39 and Raman spectroscopy. 13,[40][41][42][43][44][45] The former two methods both require the fabrication of test structures (and hence are destructive), and they have spatial resolutions on the order of hundreds of micrometers. Lab source XRD does not require any additional fabrication for stress evaluation but also suffers from spatial resolutions that are typically on the order of hundreds of micrometers.…”