Study on optimal growth conditions of a-plane GaN grown on r-plane sapphire by metal-organic chemical vapor deposition

Effects of initial conditions and growth temperature on the properties of nonpolar a ‐plane AlN grown by LP‐HVPE

“…The same phenomenon was found for nonpolar GaN. Ko et al [11] found that high temperature could lead to a fully coalesced a-plane GaN layer. Kusakabe and Ohkawa [12] found that the combination of buffer thickness and temperature is the main factor in obtaining a smooth surface because of the different effects of enhanced temperature on the lateral growth in the [1-100] and [0001] orientations.…”

“…FWHM value is smaller along the [0001] directions than that along the [1-100] direction. These data indicate that the crystallographic mosaicity is anisotropic because of the anisotropic in-plane growth rate of (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) AlN. This difference is reduced with increasing temperature up to 1450 o C, partly due to the decreased difference in the lateral rates between two in-plane directions at enhanced temperature.…”

“…The a-plane AlN layers exhibit a complex strain pattern because of the fact that the AlN is stressed in the [1-100] AlN direction , whereas it is stress-free in the [11][12][13][14][15][16][17][18][19][20] AlN growth direction. The hexagonal unit cell of AlN turns into an orthorhombic cell with three independent lattice parameters, a, b, and c. To determine the lattice parameters a, and b (the (1-100) plane-distance d 1-100 ) of the layers, various AlN reflections were measured by XRD 2θ/ω scanning under symmetric (11)(12)(13)(14)(15)(16)(17)(18)(19)(20), and (10-10) diffraction geometries. For every reflection (hkil) Bragg's law was applied to derive the lattice plane spacing d hkil from the Bragg angle θ hkil .…”

Influence of slight misorientations of r ‐plane sapphire substrates on the growth of nonpolar a ‐plane GaN layers via HVPE

“…3 Results and discussion 3.1 MOVPE template Nonpolar a-plane GaN grown by MOVPE usually shows a typical morphology: a stripe like feature along the c direction and some surface pits [12]. We observed a reduced and more homogenous surface roughness for negative miscuts (samples a, b) whereas for positive miscuts the stripe like pattern becomes more pronounced and surface defects start to develop (d, e).…”

Direct MOVPE‐ and MBE‐growth of a‐plane GaN on r‐plane sapphire

“…Recently groups started to grow directly on r-plane sapphire [5,6]. In this paper we report on a thorough investigation of the different growth stages and coalescence processes in MOVPE and MBE.…”