Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures

Abstract

We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ∼70° for Al0.13Ga0.87N/GaN (h0h̄1) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1−xN/GaN heterostructures.

Luminescence behavior of semipolar (101¯1) InGaN/GaN “bow-tie” structures on patterned Si substrates

“…The length of these faint dark lines varies and is estimated to be 3À4 μm, based on several CL images. They are likely to be misfit dislocations, which appear as dark lines in pan-and monochromatic CL images in semipolar and nonpolar III-nitride structures [24][25][26] and will be discussed further with the ECCI results. Similar (1 101) InGaN/GaN MQW structures were investigated in Ref.…”

Misfit Stress Relaxation in α-Ga2O3/α-Al2O3 Heterostructures via Formation of Misfit Dislocations

“…In the model proposed below, we implement the approach developed for describing misfit stress relaxation in wurtzite-type heterostructures [20,21] using the hexagonal geometry of a unit cell of the contacting α-Ga 2 O 3 and α-Al 2 O 3 phases but introducing additional constant C 14 into corresponding equations. Let us consider the process of misfit stress relaxation in α-Ga 2 O 3 /α-Al 2 O 3 heterostructures with different orientations of the film growth due to formation of MDs in the geometry and with designations presented in Fig.…”

Strain compensated superlattices on m-plane gallium nitride by ammonia molecular beam epitaxy

“…This is consistent with the prismatic MD formation. 14,15 Multiplying the projection of the Burger's vector along the 11 20 ½ a-direction by this spacing gives an estimate of the plastic relaxation, in this case merely $0.0016% (plastic relaxation p ¼ 1:6 Â 10 À5 ). By the 20-period sample, cracking was observed on (0001) planes (crack traced along the 11 20 ½ a-direction).…”

“…A 10 period 1.5 nm Al 0.5 Ga 0.5 N/4 nm GaN sample (with an additional AlGaN 11th barrier for confinement) with a 20 nm GaN cap, and a 10 period 6.1 nm In 0.1 Ga 0.9 N/4 nm GaN sample with a 10 nm GaN cap were grown. While compositions, number of periods and layer thicknesses were chosen for subsequent spectroscopic measurements, 27 14,15 Even lower MD linear densities of 2.0 Â 10 2 cm À1 and 1.8 Â 10 2 cm À1 , for the InGaN/GaN and AlGaN/GaN SLs, respectively, indicate that the sign of the average SL strain did not affect the MD formation. Additionally, while AFM RMS roughness of both samples was again sub-nanometer, a meandering morphology was evident in the In 0.10 Ga 0.90 N/ GaN SL, a consequence of the lower temperature required for higher composition InGaN growth.…”

“…10 On semipolar orientations, shear stress on both the (0001) c-plane and the 10 10 f g m-planes is possible, and both basal and prismatic MDs are observed. [11][12][13][14][15][16] In m-plane oriented strained layers, there is no shear stress on the vertically oriented (0001) plane, but there is shear stress on the inclined 10 10 f g prismatic m-planes for strained layers, meaning only prismatic MDs are observed. 5,6,16 The manner through which strain is relieved is a major issue in III-Nitride heterostructures as there are large lattice mismatches between the binary endpoints of the system; À2.4% and 11.2% for AlN and InN, respectively, on GaN along the 11 20 ½ a-direction and À3.9% and 10.0% for AlN and InN, respectively, on GaN along the [0001] c-direction.…”