A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors

We examine the Moss–Burstein effect for InN and demonstrate an independent method for determing its magnitude for high carrier concentration material. Consequently it is shown that the extent of the Moss–Burstein effect is less than 0.72 eV for a high carrier concentration sample with a 1.88 eV absorption edge. Early results are also provided for high band‐gap low carrier concentration InN films that can be grown reprodcibly, vindicating the work of early groups in the field. The role of stoichiometry is examined in relation to point defects that appear to be common to many forms of InN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Gallium nitride and indium nitride films have been grown by remote plasma enhanced chemical vapor deposition (RPECVD) at temperatures between 570 and 650 °C for GaN and between 350 and 570 °C for InN on different substrates. For GaN vast improvements in film morphology and quality have resulted from reductions in background impurities when compared to previous reports. Epitaxial material can now be grown at 650 °C under optimized growth conditions. Columnar growth still occurs for growth on some substrates, however film coalescence is observed when using appropriate buffer layers and epitaxial growth can also be observed. High resolution SEM images show examples of this. The root-mean-square surface roughness of epitaxial samples, as measured using atomic force microscopy, shows values of as little as 10 Angstroms. While X-ray diffraction shows that these surfaces are not amorphous but have a strong (0001) preferred axis with FWHM limited by instrumental effects to (2θ) 0.085 degrees. The improvement in film quality has allowed heavily doped n-type films to be grown with an electron mobility of 160 cm 2 /V·s for a carrier concentration of ~ 1x1019 cm -3 at 650 °C. Moss-Burstein shifted absorption data confirms the high doping level. For InN film growth by RPECVD, columnar growth is commonly observed in the temperature region of interest for films grown directly on sapphire, however film coalescence and epitaxial films are also observed for this material. X-ray diffraction indicates very sharp (0002) peaks with FWHM of (2θ) 0.07 degrees. High resolution SEM images show examples of film morphology at different growth temperatures. Electron backscattered diffraction images indicate a wurtzite structure even for InN films with strong deviations from the accepted lattice parameters. 1 Introduction Intensive work on metal-nitride film growth at low temperatures has been carried out over the last two decades at Macquarie University using remote plasma enhanced laser induced chemical deposition as described elsewhere [1][2][3]. This deposition method is based on a conventional metalorganic CVD growth but allows deposition of GaN and its alloys at lower temperature 350-670 °C. An excimer laser and a microwave plasma remote from the substrate holder enhance dissociation of gas molecules into free radicals. Low temperature metal-nitride growth has some practical advantages. These include the use of lower cost equipment and substrates, the possibility of using temperature sensitive buffer layers such as ZnO, the lower diffusion of impurities and shaper interfaces when growing thin layers, and lower thermal stress between the metal-nitride film and the substrate. The main inconveniences are weaker film adhesion to the substrate and the possibility of higher incorporation of hydrogen, oxygen and carbon during growth. Considerable work has been done on crystal size and oxygen segregation in these films [4]; on the recrystallization prospects of GaN [5]; there has been a detailed comparison of GaN grown on quartz