Self-generated microcracks in an ultra-thin AlN/GaN superlattice interlayer and their influences on the GaN epilayer grown on Si(110) substrates by metal–organic chemical vapor deposition

Shen, Xu–Qiang; Takahashi, Tokio; Matsuhata, Hirofumi; Ide, Toshihide; Shimizu, Mitsuaki

doi:10.1039/c5ce00929d

Cited by 11 publications

(7 citation statements)

References 25 publications

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“…In the case of sample B, in the initial stage of AlN/GaN SLs growth, the Al adatoms are difficult to be incorporated into the epilayer because of the large tensile stress coming from GaN template. As the growth continues, tensile stress is dramaticly released due to the generation of misfit dislocations and cracks in the AlN/GaN SLs 15 18 19 20 21 , as shown in Fig. 4(c–f) .…”

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confidence: 99%

Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

Qin

et al. 2016

Sci Rep

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Two AlGaN samples with different strain were designed to investigate mechanism of stress-driven composition evolution. It is discovered that AlGaN grown on AlN or (AlN/GaN superlattices (SLs))/GaN both consist of two distinct regions with different compositions: transition region and uniform region, which is attributed to the compositional pulling effect. The formation of the transition region is due to the partial stress release caused by the generation of misfit dislocations near the hetero-interface. And the Al composition in the uniform region depends on the magnitude of residual strain. The difference in relaxation degree is 80.5% for the AlGaN epilayers grown on different underlayers, leading to a large Al composition difference of 22%. The evolutionary process of Al composition along [0001] direction was investigated in detail.

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confidence: 99%

Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

Qin

et al. 2016

Sci Rep

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“…Due to the large lattice mismatch and thermal mismatch between GaN and Si substrates, it is challenging to grow high-quality and stress-free GaN-based epilayers. Several complicated stress-control approaches such as patterned Si substrate technology 10 , LT-AlN 11 , AlN/GaN superlattice 12 13 , and compositionally graded AlGaN layer 14 15 have been proposed to achieve crack-free GaN based heterostructures. However, the crystalline quality (defects and residual stress), as well as uniformity issues still remain, especially for growth onto large diameter substrates.…”

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confidence: 99%

Growth of high quality and uniformity AlGaN/GaN heterostructures on Si substrates using a single AlGaN layer with low Al composition

Cheng

Yang

Sang

et al. 2016

Sci Rep

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By employing a single AlGaN layer with low Al composition, high quality and uniformity AlGaN/GaN heterostructures have been successfully grown on Si substrates by metal-organic chemical vapor deposition (MOCVD). The heterostructures exhibit a high electron mobility of 2150 cm2 /Vs with an electron density of 9.3 × 10 12 cm −2 . The sheet resistance is 313 ± 4 Ω/◻ with ±1.3% variation. The high uniformity is attributed to the reduced wafer bow resulting from the balance of the compressive stress induced and consumed during the growth, and the thermal tensile stress induced during the cooling down process. By a combination of theoretical calculations and in situ wafer curvature measurements, we find that the compressive stress consumed by the dislocation relaxation (~1.2 GPa) is comparable to the value of the thermal tensile stress (~1.4 GPa) and we should pay more attention to it during growth of GaN on Si substrates. Our results demonstrate a promising approach to simplifying the growth processes of GaN-on-Si to reduce the wafer bow and lower the cost while maintaining high material quality.Recently, AlGaN/GaN heterostructures grown on Si substrates have attracted much attention for high power, high frequency, and high temperature applications [1][2][3][4] . These can offer several advantages such as large wafer size, high thermal conductivity, low cost, and great potential of the compatibility with existing processing technologies developed for Si integrated circuits [5][6][7][8] . Despite the promising applications, GaN-on-Si technology is facing reproducibility and reliability issues, which are likely to be related to growth processes and crystalline quality (defects and residual stress) 1,9 . Due to the large lattice mismatch and thermal mismatch between GaN and Si substrates, it is challenging to grow high-quality and stress-free GaN-based epilayers. Several complicated stress-control approaches such as patterned Si substrate technology 10 , LT-AlN 11 , AlN/GaN superlattice 12,13 , and compositionally graded AlGaN layer 14,15 have been proposed to achieve crack-free GaN based heterostructures. However, the crystalline quality (defects and residual stress), as well as uniformity issues still remain, especially for growth onto large diameter substrates.For the method with compositionally graded buffers, three step-graded AlGaN (with Al composition of about 75%, 50% and 25%) or multiple step-graded AlGaN buffers with thickness up to 1 μm are generally used [15][16][17] . The main purpose of this method is to slow down the relaxation rate of compressive stress by decreasing the lattice mismatch between the two neighbouring layers. There is thus a larger compressive stress accumulated in the GaN layer during the growth at high temperature. One issue in this case with thick buffers is that the wafer is convexly bowed. As a result, it will significantly affect the wafer uniformity during the subsequent growth. Another issue is that the growth rate of AlGaN ternary alloy is generally lower than that of GaN layer an...

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“…21) This structure can be used not only as a barrier layer for heterostructure fieldeffect transistors (HFETs) 22) but also as a relaxation layer for GaN growth on Si substrates. 8,[23][24][25][26] The thicknesses of the AlN and GaN layers in the SL structure are from 1.0 to 4.0 nm, which are much smaller than those in conventional AlN= (Al,Ga)N SL structures. 27,28) The growth of such a thin periodic SL is sensitive to the strain, especially in highly strained systems such as those with III-nitrides grown on Si substrates.…”

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confidence: 94%

Impact of strain state on the ultrathin AlN/GaN superlattice growth on Si(110) substrates by metalorganic chemical vapor deposition

Shen

Takahashi

Ide

et al. 2017

Jpn. J. Appl. Phys.

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We investigate the effect of strain state on ultrathin AlN/GaN superlattice (SL) growth by metalorganic chemical vapor deposition. It is found that the strain state (tensile or compressive) plays a role in periodic structure formation. A well-ordered SL growth with excellent periodicity can be realized under a tensile strain. However, a disordered SL structure is formed under a compressive strain. Furthermore, the ordered SL growth can be restored by inverting the strain state. Our findings show the importance of strain engineering in nanoscale structure growth.

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Self-generated microcracks in an ultra-thin AlN/GaN superlattice interlayer and their influences on the GaN epilayer grown on Si(110) substrates by metal–organic chemical vapor deposition

Cited by 11 publications

References 25 publications

Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

Mechanism of stress-driven composition evolution during hetero-epitaxy in a ternary AlGaN system

Growth of high quality and uniformity AlGaN/GaN heterostructures on Si substrates using a single AlGaN layer with low Al composition

Impact of strain state on the ultrathin AlN/GaN superlattice growth on Si(110) substrates by metalorganic chemical vapor deposition

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