Determination of the Al mole fraction and the band gap bowing of epitaxial AlxGa1−xN films

AlxGa1−xN alloys were grown on c-plane sapphire by plasma-induced molecular beam epitaxy. The Al content x was varied over the whole composition range (0⩽x⩽1). The molar Al fraction was deduced from x-ray diffraction and for comparison by elastic recoil detection analysis. The composition of the alloys calculated from the lattice parameter c underestimates x. This is due to a deformation of the unit cell. The exact Al mole fraction and the biaxial strain of the alloys can be calculated by an additional determination of a, using asymmetric reflections. The results obtained by x-ray diffraction and elastic recoil detection provide evidence for the validity of Vegard’s law in the AlGaN system. In addition, the deviation of the band gap from a linear dependence on x was investigated. We found a downward bowing with a bowing parameter b=1.3 eV.

[1]  Isamu Akasaki,et al.  Optical Properties of Strained AlGaN and GaInN on GaN , 1997 .

[2]  Kusunoki.  Volume-expansion-induced lattice instability and solid-state amorphization. , 1996, Physical review. B, Condensed matter.

[3]  H. Morkoç,et al.  GaN, AlN, and InN: A review , 1992 .

[4]  G. Dollinger,et al.  Depth microscopy at interfaces , 1994 .

[5]  I. Akasaki,et al.  Edge emission of AlxGa1−xN , 1986 .

[6]  K. Tsubouchi,et al.  Zero-Temperature-Coefficient SAW Devices on AlN Epitaxial Films , 1985, IEEE Transactions on Sonics and Ultrasonics.

[7]  Alan Francis Wright,et al.  Bowing parameters for zinc‐blende Al1−xGaxN and Ga1−xInxN , 1995 .

[8]  S. Nakamura,et al.  High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures , 1995 .

[9]  R. French,et al.  Vibrational Spectroscopy of Aluminum Nitride , 1993 .

[10]  G. Dollinger,et al.  High resolution depth profiling of light elements , 1992 .

[11]  S. Zembutsu,et al.  Substrate‐orientation dependence of GaN single‐crystal films grown by metalorganic vapor‐phase epitaxy , 1987 .

[12]  Takashi Mukai,et al.  Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes , 1995 .

[13]  Segall,et al.  Electronic structure and equilibrium properties of GaxAl1-xN alloys. , 1993, Physical review. B, Condensed matter.

[14]  M. Khan,et al.  Properties and ion implantation of AlxGa1−xN epitaxial single crystal films prepared by low pressure metalorganic chemical vapor deposition , 1983 .

[15]  A. Wee,et al.  Development of chemical beam epitaxy for the deposition of gallium nitride , 1995 .

[16]  Theeradetch Detchprohm,et al.  Relaxation Process of the Thermal Strain in the GaN/α-Al2O3 Heterostructure and Determination of the Intrinsic Lattice Constants of GaN Free from the Strain , 1992 .

[17]  Isamu Akasaki,et al.  Energy band‐gap bowing parameter in an AlxGa1−x N alloy , 1987 .

[18]  Joseph A. Miragliotta,et al.  High quality self‐nucleated AlxGa1−x N layers on (00.1) sapphire by low‐pressure metalorganic chemical vapor deposition , 1994 .

[19]  S. Misawa,et al.  Properties of AlxGa1−xN films prepared by reactive molecular beam epitaxy , 1982 .

[20]  Izabella Grzegory,et al.  Elastic constants of gallium nitride , 1996 .

[21]  S. Nakamura,et al.  Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure blue‐light‐emitting diodes , 1994 .

[22]  A. Boccara,et al.  Sensitive photothermal deflection technique for measuring absorption in optically thin media. , 1980, Optics letters.