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VLSI Scaling and Fabrication
Published in Manoj Kumar Majumder, Vijay Rao Kumbhare, Aditya Japa, Brajesh Kumar Kaushik, Introduction to Microelectronics to Nanoelectronics, 2020
Manoj Kumar Majumder, Vijay Rao Kumbhare, Aditya Japa, Brajesh Kumar Kaushik
In the modern VLSI technology, the term epitaxy is derived from the Greek epi, means above, and taxis, an ordered manner that defines the creation of one or more thin crystalline layers in ordered orientation above the substrate [30]. Based on the composition of the substrate and the layer, it can be classified as homo-epitaxy and hetero-epitaxy. If the thin epitaxy layer is made up of the same material as the substrate, it is known as homo-epitaxy, whereas in hetero-epitaxy the epitaxy layer is of a material different from the substrate [31]. The epitaxial growth methodology is used to grow the highly purified single crystalline material that was first introduced by Royer in 1928. The electrical and optical properties can be precisely controlled using the techniques other than the bulk ones. There are several epitaxy methodologies available to form high-quality epitaxial growth, such as vapor-phase epitaxy (VPE) and molecular beam epitaxy (MBE).
Structure of Bipolar Junction Transistor
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
Advances in technology ensure that the variants improve on the previous meeting-specific requirements like low noise figures and high gain, particularly at millimeter-wave frequencies. Prominent variants are gallium arsenide (GaAs) substrate-based metal-semiconductor FET (MESFET), high-electron mobility transistor (HEMT), and pseudomorphic HEMT (or pHEMT). The main difference between HEMTs and MESFETs is the epitaxial layer structure. In the HEMT structure, compositionally different layers are grown in order to optimize and extend the performance of the FET. These different layers form heterojunctions since each layer has a different bandgap, see Figure 3.4. Structures grown with the same lattice constant but different bandgaps are referred to as lattice-matched HEMTs. Those structures grown with slightly different lattice constants are called pHEMTs. The MESFETs and HEMTs are grown on a semi-insulating GaAs substrate using molecular beam epitaxy (MBE), or metal–organic chemical vapor deposition (MOCVD), which is currently less common. Epitaxy is the natural or artificial growth of crystals on a crystalline substrate determining their orientation. Other commonly used names for HEMTs include MODFET (modulation-doped FET), TEGFET (two-dimensional electron gas FET), and SDHT (selectively doped heterojunction transistor).
Semiconductor Heterojunctions, Modulation-Doped Quantum Wells, and Superlattices
Published in Jyoti Prasad Banerjee, Suranjana Banerjee, Physics of Semiconductors and Nanostructures, 2019
Jyoti Prasad Banerjee, Suranjana Banerjee
Heterojunction based on two different semiconductors having different bandgaps and lattice constant is practically realized by various epitaxial techniques such as Liquid Phase Epitaxy, Vapor Phase Epitaxy, MBE, MOCVD, Ultrahigh Vacuum Chemical Vapor Deposition, etc. High quality heterojunction interface free of defects, voids, and dislocations is an essential requirement to fabricate high performance microelectronic and optoelectronic semiconductor devices like MODFETs, Heterojunction Bipolar transistors, and QWLs. During the growth of the epitaxial layer, the lattice strain arising from mismatch of lattice constant of epitaxial layer atoms with that of substrate atoms introduces defect states at the substrate–epitaxy interface.
Enhancing thermal conductivity and balancing mechanical properties of 3D-printed iPP/HDPE-based dielectric composites via the introduction of hybrid fillers and tailored crystalline structure
Published in Virtual and Physical Prototyping, 2023
Tao Yang, Jie Leng, Jiewei Hu, Pengbo Wang, Mariya Edeleva, Ludwig Cardon, Zheng Yan, Tao Wang, Jie Zhang
iPP and HDPE are two polymeric materials which are widely used all over the world due to their balanced properties and relatively low cost (Luo et al. 2017). Moreover, iPP/HDPE melt blending is one of the most used methods to toughen iPP which has poor impact strength. Under the ideal experimental condition, iPP/HDPE blends can form a special crystalline structure called an epitaxy crystalline structure which is understood as the lattice matching of iPP (010) crystal plane and PE (100) crystal plane (Battegazzore, Bocchini, and Frache 2011). The epitaxy crystalline can greatly improve impact performance of products (Gu et al. 2020; Zhou et al. 2017). However, the high crystallinity and shrinkage of both polymeric materials which would cause the intense warpage deformation of printed parts restrict their wide applications in FFF.
Heteroepitaxy of diamond semiconductor on iridium: a review
Published in Functional Diamond, 2022
Weihua Wang, Benjian Liu, Leining Zhang, Jiecai Han, Kang Liu, Bing Dai, Jiaqi Zhu
Epitaxy on a single-crystal substrate provides a feasible method for precisely controlling the grain orientation of epitaxial materials to achieve the large-area single-crystal growth. There are two basic concepts: homoepitaxy and heteroepitaxy [3, 47]. Homoepitaxy [48–50] is a method to deposit diamond film on high-quality single-crystal diamond seeds in chemical vapor deposition (CVD) reactors, which include hot-filament CVD [51], microwave-plasma CVD [52–54], DC arc plasma jet CVD [55], etc. Though the gas excitation and activation methods are slightly different, the growth process is similar [56]. To enlarge the diamond size, three-dimension growth [53, 57] and mosaic growth [51, 58–65] are generally adopted. Nad et al. [57] conducted the MPCVD growth of single crystalline diamond substrates with PCD rimless and expanding surfaces. The lateral SCD surface area increased up to two times greater than the initial seed surface area in one run. The lift-off method can be used to separate the freestanding single-crystal CVD diamond slice from the seed [66–71]. Yamada et al. [63, 64] reported a 2-in. wafer (40 × 60 mm2) growth by the mosaic growth, but the high cost and inevitable interface greatly hinder the development of this method.