Flat GaN epitaxial layers grown on Si(111) by metalorganic vapor phase epitaxy using step-graded AlGaN intermediate layers

Abstract

In this work, we report on the growth by metalorganic vapor phase epitaxy (MOVPE) of GaN layers on AlN/Si(111) templates with step-graded AlGaN intermediate layers. First, we will discuss the optimization of the AlN/Si(111) templates and then we will discuss the incorporation of step-graded AlGaN intermediate layers. It is found that the growth stress in GaN on high-temperature (HT) AlN/Si(111) templates is compressive, although, due to relaxation, the stress we have measured is much lower than the theoretical value. In order to prevent the stress relaxation, step-graded AlGaN layers are introduced and a crack-free GaN epitaxial layer of thickness .1 mm is demonstrated. Under optimized growth conditions, the total layer stack, exceeding 2 mm in total, is kept under compressive stress, and the radius of the convex wafer bowing is as large as 119 m. The crystalline quality of the GaN layers is examined by highresolution x-ray diffraction (HR-XRD), and the full-width-at-half maximums (FWHMs) of the x-ray rocking curve (0002) v-scan and (ÿ1015) v-scan are 790 arc sec and 730 arc sec, respectively. It is found by cross-sectional transmission electron microscopy (TEM) that the step-graded AlGaN layers terminate or bend the dislocations at the interfaces.

The influence of nitridation time on the structural properties of GaN grown on Si (111) substrate

“…113%) [5,7,[10][11][12][13]. Due to a large lattice mismatch, a high density of threading dislocations on the order of (10 9 -10 10 cm −2 ) exists in the GaN film on silicon substrates, which significantly affects the performance of the GaN based devices [8].…”

“…Due to a large lattice mismatch, a high density of threading dislocations on the order of (10 9 -10 10 cm −2 ) exists in the GaN film on silicon substrates, which significantly affects the performance of the GaN based devices [8]. In order to obtain crack-free highquality GaN film on Si substrate, various types of buffer layers and growth conditions as well as post-growth heat treatment processes have been proposed by different research groups [10][11][12][13][14][15][16][17]. However, the appearance of the cracks is quite random on the film, which produces significant difficulty in device applications.…”

X-ray diffraction investigation of GaN layers on Si(111) and Al2O3 (0001) substrates

“…But Si substrate is the promising one for growing III-nitrides due to their low cost, big area, high thermal conductivity and easy integration in electronics. Nevertheless, when the thickness of GaN layer exceeds 1 μm, it starts to crack, which is caused by residual stresses generated by the lattice thermal expansion mismatch between the layer and substrate [4,5].…”

The electrical, optical, and structural properties of GaN epitaxial layers grown on Si(111) substrate with interlayers

“…113%) between the GaN and the Si bring out the problems in the growth of GaN films on a Si wafer such as cracking in the epitaxial layer [5,7,[10][11][12]. Also large lattice mismatch causes high density of threading dislocations on the order of (10 9 cm −2 -10 10 cm −2 ) in the GaN film on silicon substrates, which significantly limits the performance of GaN based devices [8].…”

“…Also large lattice mismatch causes high density of threading dislocations on the order of (10 9 cm −2 -10 10 cm −2 ) in the GaN film on silicon substrates, which significantly limits the performance of GaN based devices [8]. Different research groups have proposed various types of growth conditions and buffer layers as well as post-growth heat treatment processes in order to obtain crack-free high-quality GaN film on Si substrate [10][11][12][13][14][15][16]. But, the appearance of the cracks is quite random on the film, which produces significant difficulty in device applications.…”