Heat-Transport Mechanisms in Superlattices
Heat-Transport Mechanisms in Superlattices
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DOI：
10.1002/adfm.200800984
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发表时间：
2009-02-24
影响因子：
19
通讯作者：
Jena, Debdeep
中科院分区：
文献类型：
--
作者：
Koh, Yee Kan;Cao, Yu;Jena, Debdeep
通过时域热反射率测量的（AlN）(x)-(GaN)(y)超晶格的跨平面导热系数Lambda，确定了超晶格中的热传递机制。对于在不同条件下生长的（AlN）（4.1） (nm)-(GaN)(55) （nm）超晶格，A的变化系数为2；这归因于AlN/GaN界面粗糙度的差异。在λ最低的生长条件下，（AlN）(4) (nm)-(GaN)(y)超晶格的λ随y的减小而单调减小，在y = 2.2 nm处λ = 6.35 W m(-1) K-1，比本体GaN的A小35倍。对于长周期超晶格（y > 40 nm）， AlN/GaN界面的平均热导率G与y无关，约为620 MW m(-2) K-1。当y < 40 nm时，G的表观值随y的减小而增大，在y < 3 nm时，G接近于2 GW m(-2) K-1。MeV离子轰击用于帮助确定在短周期超晶格中哪些声子负责热输运。（AlN）（4.1） (nm)-(GaN)(4.9) （nm）超晶格经2.3 MeV氩离子辐照至2 × 10（14）离子cm（-2）剂量后，其导热系数降低了
The heat transport mechanisms in superlattices are identified from the cross-plane thermal conductivity Lambda of (AlN)(x)-(GaN)(y) superlattices measured by time-domain thermoreflectance. For (AlN)(4.1) (nm)-(GaN)(55) (nm) superlattices grown under different conditions, A varies by a factor of two; this is attributed to differences in the roughness of the AlN/GaN interfaces. Under the growth condition that gives the lowest Lambda, Lambda of (AlN)(4) (nm)-(GaN)(y) superlattices decreases monotonically as y decreases, Lambda = 6.35 W m(-1) K-1 at y = 2.2 nm, 35 times smaller than A of bulk GaN. For long-period superlattices (y > 40 nm), the mean thermal conductance G of AlN/GaN interfaces is independent of y, G approximate to 620 MW m(-2) K-1. For y < 40 nm, the apparent value of G increases with decreasing y, reaching G approximate to 2 GW m(-2) K-1 at y < 3 nm. MeV ion bombardment is used to help determine which phonons are responsible for heat transport in short period superlattices. The thermal conductivity of an (AlN)(4.1) (nm)-(GaN)(4.9) (nm) superlattice irradiated by 2.3 MeV Ar ions to a dose of 2 x 10(14) ions cm(-2) is reduced by