Properties of GaN epilayers grown on misoriented sapphire substrates

Three silicon-doped 3 µm thick GaN epilayers were grown simultaneously by metalorganic chemical vapour deposition on (0001) sapphire substrates misorientated by 0°, 4° and 10° toward the m-plane (10 0). A comparative study of these epilayers was undertaken using photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), cathodoluminescence (CL) imaging, CL spectroscopy and Hall effect measurements. Low temperature PL of the 0° and 4° epilayers shows donor bound exciton (BE) emission between 3.47 and 3.48 eV and a low level of yellow band emission. The peak intensities of both emission bands are a factor of 2 higher for the 4° layer. In the 10° epilayer, the BE band is 3x stronger than in the 0° epilayer but there is no discernible yellow band. However, a number of additional bands appear at 3.459, 3.417, 3.362, 3.345, 3.309, and 3.285 eV. These bands, some of which are acceptor related, may be attributed to the presence of structural defects in this epilayer, pointing to an abrupt degradation of its structural quality compared to the others. This degradation is confirmed by AFM studies. On a 20 µm x 20 µm image the 0° and 4° epilayers exhibit smooth surface morphologies, while the 10° epilayer shows a high density of hexagonal pits. Finally, SEM images reveal the surface of the 10° epilayer to be “streaked” and pitted. Low temperature CL images at 3.48 eV (bound exciton region) show random spotty emission, while those at 3.28 eV and 3.41 eV exhibit a streaky appearance similar to the SEM image. This suggests that these luminescence bands are indeed associated with structural defects.

[1]  K. Thonke,et al.  Donor-Acceptor Pair Transitions in GaN , 1997 .

[2]  Jinsang Kim,et al.  Structural properties of ZnSe layers grown on (001) GaAs substrates tilted toward [110] and [010] , 1997 .

[3]  A. Ishibashi,et al.  Metalorganic Vapor Phase Epitaxy Growth of a High-Quality GaN/InGaN Single Quantum Well Structure Using a Misoriented SiC Substrate , 1997 .

[4]  A. Holmes,et al.  The effect of substrate misorientation on the optical, structural, and electrical properties of GaN grown on sapphire by MOCVD , 1997 .

[5]  S. G. Bishop,et al.  Luminescence studies of GaN grown on GaN and GaN/AlN buffer layers by metalorganic chemical vapor deposition , 1996 .

[6]  S. Hersee,et al.  The role of the low temperature buffer layer and layer thickness in the optimization of OMVPE growth of GaN on sapphire , 1995 .

[7]  Y. Kawaguchi,et al.  ZnCdSe/ZnSe Quantum-Well Laser Diode on a (711)A GaAs Substrate , 1994 .

[8]  Takashi Mukai,et al.  Si- and Ge-Doped GaN Films Grown with GaN Buffer Layers , 1992 .

[9]  T. Fukui,et al.  Step-density dependence of growth rate on vicinal surface of MOCVD , 1991 .

[10]  Shuji Nakamura,et al.  GaN Growth Using GaN Buffer Layer , 1991 .

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

[12]  Sadafumi Yoshida,et al.  Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN‐coated sapphire substrates , 1983 .

[13]  H. M. Manasevit,et al.  The Use of Metalorganics in the Preparation of Semiconductor Materials IV . The Nitrides of Aluminum and Gallium , 1971 .

[14]  Bernard Gil,et al.  Group III nitride semiconductor compounds : physics and applications , 1998 .

[15]  C. T. Foxon,et al.  Alternative substrates for gallium nitride epitaxy: photoluminescence and morphological investigations , 1997 .

[16]  Y. T. Rebane,et al.  Dislocation Luminescence in Wurtzite GaN , 1996 .

[17]  P. G. Middleton,et al.  The morphology and cathodoluminescence of GaN thin films , 1996 .

[18]  Eugene E. Haller,et al.  Fine Structure of the 3.42 eV Emission Band in GaN , 1995 .

[19]  Inspec,et al.  Properties of group III nitrides , 1994 .

[20]  H. Amano,et al.  MOVPE growth of GaN on a misoriented sapphire substrate , 1991 .