Tutorial EQ02: Heterostructures of Various Dimensional Materials—From Epitaxy to Device Applications

The tutorial focuses on the fundamentals and applications of heterogeneously integrated structures using 1D, 2D, and 3D materials from the growth of 3D materials on 2D materials, and various lift-off technologies to heterogeneous integration of electronic/optoelectronic devices.

Remote Epitaxy: Growth of 3D Materials on 2D Materials 
Jeehwan Kim, Massachusetts Institute of Technology

The instructor will discuss a new epitaxy lift-off technique, a so-called remote epitaxy that can produce freestanding semiconductor membranes. Discussion will include 1) Remote epitaxy mechanism 2) High yield peeling mechanism 3) Reusability of the substrates 4) Economic aspect of remote epitaxy  and 5) Heterointegration of 3D materials with 2D materials for advanced heterostructuring.


van der Waals Epitaxy : Epitaxial Growth of 2D and 3D Materials 
Xinqiang Wang, Peking University

The instructor will provide the overview regarding the epitaxial growth of Nitride-based semiconductor materials by MOVPE including GaN and h-BN, and design device structures for opto-electronic devices. In addition, the tutorial will cover the fabrication of nanostructures and materials characterization. The epitaxial growth of 3D and 2D materials and characterization of them is the basis of fabrication of heterointegration systems for various device applications.


Heterostructures Built on Three-Dimensional (3D) Semiconductor 
Zhenqiang (Jack) Ma, University of Wisconsin-Madison

Heterostructures built on three-dimensional (3D) semiconductor materials are rooted in the theory conceived by Nobel Laureate Hebert Kroemer in 1957. Since then, the four classes, namely, GaAs-, InP-, Si/Ge-, and III-nitrides-based heterostructures, have revolutionized the electronics and optoelectronics that set the foundation of today’s communications, lighting, sensing, infotainment, etc. These heterostructures were universally formed by epitaxy techniques uniquely governed and enabled by the stringent requirements of lattice matching. Limited by this requirement, realizing heterostructures between lattice-mismatched semiconductors has been a decades-long obstacle, although the materials space to explore and the number of heterostructures that can be made are vast compared to its lattice-matched counterparts. In this tutorial, lattice-mismatched heterostructures, i.e., heterogeneous heterostructures, or arbitrary heterostructures, formed via semiconductor grafting based on a quantum tunneling gluing approach, are described. The tutorial will include: the history of attempts to form lattice-mismatched heterostructures; physical principles of bypassing the lattice constraints; fabrication methods and scalability; and a set of application examples that are selected from about 18 pairs of heterostructures formed between Si, Ge, GeSn, GaAs, InGaAs, AlGaAs, GaN, AlGaN, SiC, GaN, Diamond, β-Ga2O3, and CsPbBr3.

van der Waals Heterostructures
Deep Jariwala, University of Pennsylvania and Xiangfeng Duan, University of California, Los Angeles

The isolation of a growing number of two-dimensional (2D) van der Waals (vdW) materials has inspired worldwide efforts to integrate distinct 2D materials into vdW heterostructures. Over the past decade a tremendous amount of research activity has occurred in assembling disparate 2D materials into “all-2D” van der Waals heterostructures, thereby making outstanding progress on fundamental studies at 2D/2D interfaces. However, practical applications of 2D and other low-dimensional materials will require a broader integration strategy. Namely, integration of 2D materials with other self-passivated, quantum-confined, or molecular materials will be necessary. In this regard significant progress has been achieved in recent years, which involves successful integration of 2D materials with organic small molecules, quantum-dots, nanocrystals, semiconducting polymers, and inorganic nanowires, as well as carbon-nanotubes. These studies have produced interesting results, both in terms of basic science as well as in device applications including in photodetectors, logic, memory, and light emitting devices. In addition, 2D van der Waals layers have also provided a rich and interesting avenue in terms of hetero-integration with three-dimensional (3D) and bulk materials including 3D semiconductors, piezoelectrics, ferroelectrics, and magnets. The 2D/3D combinations are particularly favorable and attractive in terms of vertical integration on Silicon CMOS and enabling “More than Moore” approaches including memory, electronic-photonic integration, etc., for semiconductor chips. This tutorial will provide an overview of the progress on the above described heterostructures and their devices, focusing on the unique advantages and capabilities that each materials combination provides. It will end with a broad and forward-looking perspective on future investigation and development opportunities in mixed-dimensional heterostructures and their applications for the research community.