Characterization of crystal lattice constant and strain of GaN epilayers with different AlxGa1－xN and AlN buffer layers grown on Si(111)

Abstract

Hexagonal GaN epilayers with different AlxGa1-xN and AlN buffer layers were grown on Si(111) by metal-organic vapor phase epitaxy (MOVPE). Under the same growth conditions, the sample with four AlxGa1-xN buffer layers and one AlN buffer layer were grown on Si(111). According to the results of Rutherford backscattering (RBS)/channeling along axis, the conventional θ—2θ scans normal to GaN(0002) and (1122) plane at 0° and 180° azimuthal angles, and the reciprocal-space X-ray mapping (RSM) on GaN(1015) plane, we obtained that the crystal quality of the GaN epilayer is perfect with χmin＝1.54%. The crystal lattice constant of AlN, AlxGa1-xN and GaN epilayer has been calculated accurately, the lattice constant of GaN epilayer is almost equal to the theoretic data (aepi=0.31903nm, cepi=0.51837nm). The tetragonal distortion along the depth can got clearly from elastic strains of each layer in the normal and parallel directions, and the tetragonal distortion of GaN epilayer is nearly fully relaxed(eT=0).

Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer

“…However, for GaN heteroepitaxy on Si substrate, the large lattice mismatch and thermal mismatch between GaN and Si usually lead to high threading dislocation (TD) density and the formation of cracks in GaN layer during the cooling process. [3] Up to now, various interlayers (ILs) such as AlN IL, [4−6] AlN/GaN superlattice [7,8] and AlGaN ILs, [9−13] have been introduced into the growth of GaN epilayer to compensate the tensile stress and prevent the formation of cracks. Previously, we have reported that AlGaN IL plays a remarkable role in introducing compressive strain into the subsequently grown GaN layer and significantly reducing TD density in the GaN epilayer.…”

The effect of single AlGaN interlayer on the structural properties of GaN epilayers grown on Si (111) substrates

“…However, for GaN heteroepitaxy on Si substrate, the large lattice mismatch and thermal mismatch between GaN and Si usually lead to high threading dislocation (TD) density and the formation of cracks when cooling down to room temperature from the growth temperature. [3] Up to now, various interlayers (ILs) such as AlN IL, [4−6] AlN/GaN superlattice [7,8] and step-graded or composition-graded AlGaN IL, [9−13] have been introduced into the growth of GaN epilayer to compensate for the large thermal tensile stress and prevent the formation of cracks. Among these ILs, AlN IL reduces the crack density and concurrently introduces extra edge-type TDs in the top GaN films, AlN/GaN superlattice or step-graded AlGaN IL growth needs a precise control of layer parameters and is very much dependent on the experimental system.…”

Structural Analysis of InxGa1−xN/GaN MQWs by Different Experimental Methods

“…Currently, In x Ga 1−x N/GaN multi-quantum wells (MQWs) have been attracting much research interest, acting as active layers in high brightness III-nitride laser emitting diodes (LEDs) and cw blue-green laser diodes. [1,2] In x Ga 1−x N/GaN heterostructures can exhibit intense photoluminescence (PL) despite a high density of dislocations and defects. [3] A great deal of research effort has been focused on In x Ga 1−x N/GaN MQWs structures.…”