On the anisotropic wafer curvature of GaN-based heterostructures on Si(1 1 0) substrates grown by MOVPE

• Published in: Journal of crystal growth Vol. 315; no. 1; pp. 220 - 223
• Main Authors: Mauder, C., Booker, I.D., Fahle, D., Boukiour, H., Behmenburg, H., Rahimzadeh Khoshroo, L., Woitok, J.F., Vescan, A., Heuken, M., Kalisch, H., Jansen, R.H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2011; Elsevier
• Subjects: A1. Stresses; A1. X-ray diffraction; A3. Metalorganic vapor phase epitaxy; Aluminum nitride; Anisotropy; B1. Nitrides; B2. Semiconducting III–V materials; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Cracks; Cross-disciplinary physics: materials science; rheology; Curvature; Exact sciences and technology; Gallium nitrides; Insertion; Materials science; Mathematical analysis; Methods of deposition of films and coatings; film growth and epitaxy; Other semiconductors; Physics; Specific materials; Strain; Theory and models of film growth; Vapor phase epitaxy; growth from vapor phase; Wafers; A3. Metalorganic vapor phase epitaxy; B1. Nitrides; B2. Semiconducting III–V materials; A1. X-ray diffraction; A1. Stresses; Nucleation; Roughness; VPE; XRD; Gallium nitride; Thin films; Relaxation; Wafers; Mismatch lattice; Stress effects; Silicon; B2. Semiconducting III―V materials; Surface morphology; Aluminium nitride; Cracking; Mechanical properties; III-V compound; Film growth; Tensile stress; Anisotropy; MOVPE method; Superlattices; Growth mechanism; Crystal faces; Curvature; Heterostructures; III-V semiconductors
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2010.08.049

We highlight the challenges of GaN growth on (1 1 0)-oriented Si substrates with respect to the substrate-induced anisotropic strain state. A 5:4 lattice matching relationship, which is valid for AlN and Si(1 1 1), is also expected for AlN on Si(1 1 0) along the [1 1 –2 0]AlN/[1 −1 0]Si direction. This reduces the effective lattice mismatch for AlN on Si(1 1 0) along [1 1 –2 0] AlN/[1 −1 0] Si from 23.4% to −1.3% (compressive), while in the [1 −1 0 0] AlN/[0 0 1] Si direction, the mismatch value remains at 0.7% (tensile). The opposite signs of the two mismatch values lead to an anisotropic strain state of the deposited AlN and GaN films, which makes it difficult to balance the tensile strain induced by thermal mismatch. For a simple growth scheme using 1 μm GaN on top of a 40 nm AlN layer, this situation is reflected in an aspherical wafer curvature, anisotropic X-ray diffraction (XRD) Ω scan full width at half maximum (FWHM) values, greater surface roughness and cracking, predominantly occurring parallel to the [1 1 –2 0] direction. The anisotropic XRD FWHM may be explained by a strain-induced anisotropic nucleation mechanism for GaN on AlN. Also, a partial relaxation of the GaN film during growth caused by very high tensile strain along [1 –1 0 0] AlN/[0 0 1] Si is assumed to contribute to the XRD anisotropy. The insertion of an AlN/GaN superlattice structure in between the AlN and GaN films inhibits this relaxation process and leads to a smoother surface morphology with less visible cracks.