Surface morphology of AlN buffer layer and its effect on GaN growthby metalorganic chemical vapor deposition

Abstract

The in situ optical reflectivity measurements are employed to monitor the GaN epilayer growth process above low-temperature AlN buffer layer on c-plane sapphire substrate by metalorganic chemical vapor deposition. It is found that the lateral growth of GaN islands and their coalescence is promoted in the initial growth stage if the AlN buffer layer is treated with a long annealing time and has an optimal thickness: As confirmed by atomic force microscopy observations, the quality of GaN epilayers is closely dependent on the surface morphology of AlN buffer layer, especially the grain size and nuclei density after the annealing treatment.

Effects of AlN nucleation layers on the growth of AlN films using high temperature hydride vapor phase epitaxy

“…Changes on surface morphology, re-distribution of NI's density, size and height are observed after the HT-treatment could also explain a part of the thickness reduction. In fact, a too thin or too thick AlN buffer layer will lead to a deteriorated quality of AlN films [29]. The thickness of NLs before HT-AlN layers growth will definitely have an important impact on the HT-AlN layer quality.…”

Defect evolution and accompanied change of electrical properties during the GaN growth by metalorganic chemical vapor deposition

“…The real-time in situ optical reflectivity measurements are employed to monitor the whole growth stages of GaN materials [10][11][12]. Fig.…”

“…After the deposition of low-temperature buffer layer, the growth process of GaN epilayers is often separated into three steps: (i) three-dimensional (3D) island growth, (ii) island coalescence and lateral growth, and (iii) quasi two-dimensional (2D) growth [10][11][12]. From Fig.…”

“…According to the growth mechanism, in the process of 3D island growth, there are a lot of dislocations in the GaN material, so sample A has a high dislocation density. In the followed process of island coalescence and lateral growth, a lot of dislocations will bend and even annihilate [10][11][12]16,17], leading to an increasing volume of defect-free columnar domains. The dislocation density of samples will also reduce during this process.…”

Study of buffer and epitaxy technology in two-step growth of aluminium nitride

“…The variety of nucleation temperature will change the size and density of crystal nucleus of buffer layer, and thus influence the quality of AlN epilayer [10] . Different samples were grown on different AlN buffers that were deposited at various nucleation temperatures in the range of 600℃ -800℃, keeping other conditions unchanged.…”