No abstract

A freestanding GaN substrate over 2 inches in size was successfully prepared for the first time by hydride vapor phase epitaxy (HVPE) using GaAs as a starting substrate. In the experiment, a GaAs (111)A substrate with a SiO 2 mask pattern on its surface was used. A thick GaN layer was grown on the GaAs substrate at 1030 • C through the openings in the SiO 2 mask. By dissolving the GaAs substrate in aqua regia, a freestanding GaN substrate about 500 µm thick was obtained. The fullwidth at half maximum (FWHM) in the ω-mode X-ray diffraction (XRD) profile of GaN (0002) plane was 106 arcsec. The dislocation density of the GaN substrate obtained was determined to be as low as 2 × 10 5 cm −2 by plan-view transmission electron microscopy (TEM). Hall measurements revealed the n-type conductivity of the GaN substrate with typical carrier concentration and carrier mobility of 5 × 10 18 cm −3 and 170 cm 2 ·V −1 ·s −1 , respectively.

An analysis of the metalorganic vapor-phase epitaxial (MOVPE) growth from a thermodynamic point of view is described for binary nitrides: GaN, InN and AlN. The equilibrium partial pressures are calculated for the input V/III ratios. It is shown that there are three deposition modes, growth, etching and droplet modes, depending on the partial pressures. The phase diagram for deposition is also calculated for the parameters of growth temperature and extent of ammonia decomposition. The conditions required for InN growth are discussed.

A thermodynamic analysis of alloy composition is described for metalorganic vapor phase epitaxy (MOVPE) of In x Ga1- x N. The vapor-solid distribution relationship is discussed in comparison with the experimental data reported in the literature. It is shown that the solid composition of In x Ga1- x N alloy grown by MOVPE is thermodynamically controlled. The origin of the deviation of the solid composition from the linear relation is also discussed.

No abstract

No abstract

A thermodynamic analysis of hydride vapor phase epitaxy (HVPE) is described for GaN. The partial pressures of gaseous species in equilibrium with GaN are calculated for temperatures, input GaCl partial pressures, input V/III ratios and mole fractions of hydrogen relative to the inert gas atoms. It is shown that the deposition of GaN is significantly influenced by the hydrogen mole fraction in the carrier gas. The growth rate is discussed in comparison with the experimental data reported in the literature. It is shown that the growth rate of GaN grown using HVPE is thermodynamically controlled.

No abstract