Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides
Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides
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DOI：
10.1073/pnas.1405435111
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发表时间：
2014-04-29
影响因子：
11.1
通讯作者：
Javey, Ali
中科院分区：
文献类型：
--
作者：
Fang, Hui;Battaglia, Corsin;Javey, Ali
半导体异质结是激光器、发光二极管、太阳能电池和高电子迁移率晶体管等重要器件应用的基础平台。与传统异质结构类似，层状过渡金属二卤化物异质结构可以通过将单个单层组装成功能多层结构来设计和构建，但原则上具有原子尖锐的界面、没有原子的互扩散、数字控制的层状元件以及没有晶格参数限制。然而，这种新型的范德华(VDW)半导体异质结的光电行为在单层极限下是未知的。具体地说，在这种异质双分子膜中，光学跃迁是空间直接的还是间接的，这在实验上是未知的。在这里，我们研究了由单层WSe2和MoS2构建的人造半导体异质结。我们观察到光致发光峰和最低吸收峰之间类似于100 meV的大的斯托克斯式位移，这与具有空间直接吸收但空间间接发射的第二类带排列一致。值得注意的是，这种空间间接跃迁的光致发光强度很强，表明电荷载流子的层间耦合很强。通过在VDW带隙中插入介质层，可以很容易地调谐异质界面上的这种耦合，该带隙由六方BN组成。因此，这种层间耦合的一般性质在能带工程中提供了一个新的自由度，并有望产生一类具有可调光电特性的新的半导体异质结，并具有定制的复合层。
Semiconductor heterostructures are the fundamental platform for many important device applications such as lasers, light-emitting diodes, solar cells, and high-electron-mobility transistors. Analogous to traditional heterostructures, layered transition metal dichalcogenide heterostructures can be designed and built by assembling individual single layers into functional multilayer structures, but in principle with atomically sharp interfaces, no interdiffusion of atoms, digitally controlled layered components, and no lattice parameter constraints. Nonetheless, the optoelectronic behavior of this new type of van der Waals (vdW) semiconductor heterostructure is unknown at the single-layer limit. Specifically, it is experimentally unknown whether the optical transitions will be spatially direct or indirect in such heterobilayers. Here, we investigate artificial semiconductor heterostructures built from single-layer WSe2 and MoS2. We observe a large Stokes-like shift of similar to 100 meV between the photoluminescence peak and the lowest absorption peak that is consistent with a type II band alignment having spatially direct absorption but spatially indirect emission. Notably, the photoluminescence intensity of this spatially indirect transition is strong, suggesting strong interlayer coupling of charge carriers. This coupling at the hetero-interface can be readily tuned by inserting dielectric layers into the vdW gap, consisting of hexagonal BN. Consequently, the generic nature of this interlayer coupling provides a new degree of freedom in band engineering and is expected to yield a new family of semiconductor heterostructures having tunable optoelectronic properties with customized composite layers.