Erik Jonsson School of Engineering & Computer Science Materials Science and Engineering UT Dallas

















In our laboratory, we use molecular beam epitaxy (MBE) to enable the growth of extremely precise, low defect materials with unique properties, and we couple that with advanced materials characterization and device fabrication techniques.  Our goal is to develop a fundamental understanding of the issues associated with heterogeneous materials integration, low-power and high performance logic and memory devices, and energy storage. We have established collaborations with other researchers in Materials Science, Physics, Electrical Engineering, and Chemistry.  We work closely with researchers at NIST, Sandia, and the Army Research Labs and from other universities (for example UC Berkeley, Rutgers, Purdue, UT-Austin, Georgia Tech, University College Cork), and we maintain ongoing projects and collaborations with U.S. and International Industries (Texas Instruments, Intel, TSMC, Samsung, Applied Materials, SRC, SEMATECH).  

In our lab, a unique multi-chamber MBE has been established with each of the VG-Semicon growth chambers linked together with a UHV transfer tube system operating at a base pressure of about 10-11 mbar.  II-VI growth is performed in a V80H growth chamber equipped with two vertical e-beam evaporators, enabling the growth of high melting temperature metals such as Hf, Mo, W, and Fe, in addition to effusion cell evaporation of Se, Te, Zn, Bi, and Be.  The two e-beam evaporators allow for TMD and topological insulator heterostructure growth as well as mixed transition metal TMDs and magnetic doping, providing significant flexibility in material and device design. The chamber is also equipped with ZnCl2 and nitrogen plasma sources for doping and surface functionalization.  The III-V chamber is also a V80H with recently upgraded hardware and software to provide state-of-the-art growth capabilities including In, Ga, As, B, Al, and N compounds as well as in-situ H-cleaning and Be and Si doping.  The Group IV chamber, a V90S, is used to grow Si, Ge, and Sn epitaxial films,SiSnGe compounds, and strained heterostructures.  The vertical growth chamber in this system incorporates electron-beam evaporators and effusion cells for Sb and B doping.  Preparation chambers with high temperature heating stages are available for each material system.  Each growth chamber is equipped with in-situ RHEED allowing us to assess the growth quality in real-time.

MBE System

These MBE capabilities allow us to study materials that are important for a number of applications such as:

  • Transition Metal Dichalcogenides:HfSe2  We are investigating the MBE growth and characterization of an exciting class of 2-Dimensional materials known as transition metal dichalcogenides (TMD).  TMDs are layered materials somewhat analogous in that respect to graphene.  Unlike graphene though, through the strategic selection of transition metal and chalcogen, we can tune the electronic properties of these materials making semiconductors with useful electronic properties.  As layered 2D materials, these materials can be grown on many different substrates through weak van der Waals interactions, drastically reducing the impact of lattice mismatch on the quality of the crystal growth.  We are currently focused on growing heterostructures (see Figure to the left) of these materials with useful band alignments for applications such as the broken-gap tunnel FET and the BiSFET.  With our two e-beam evaporators we have succesfully grown Hf and W based dichalcogenides including mixed TM and mixed chalcogen TMDs.  We have also started to investigate magnetic doping of these TMDs.
  • Hexagonal Boron Nitride (h-BN): We are also growing another layered, hexagonal 2D material by MBE that has insulating properties, h-BN.  We use a high temperature effusion cell for very slow evaporation of boron in conjunction with a plasma nitridation source.  The h-BN is being utilized as an interlayer to decouple the TMD wavefunctions in tunnel FETs and as an insulating substrate for all 2D material heterostructures.
  • Topological Insulators:Bi2Se3 RHEED  We are growing topological insulators (TIs), an interesting class of materials that have topologically protected spin polarized carriers on their surfaces or edges.  We are investigating the MBE growth of both 3D TIs (Bi2Se3) and 2D TIs (monolayer Sn and 1T' TMDs) to integrate them into novel, very low-power and high speed logic and memory devices.  We have recently demonstrated high-quality growth of Bi2Se3 (see RHEED image below) and monolayer Sn and are in the process of determining their topological properties by ARPES and STM/STS.  Coupling these materials with ferromagnets will allow us to investigate spin-transfer torque for the devices mentioned earlier.
  • Ge, InGaAs, and GaN on Si(100): We are also studying the heterogeneous integration of alternative channel materials (Ge, InGaAs, and GaN) onto a bulk Si(100) platform.  Using techniques similar to aspect ratio trapping where we use patterned trenches in oxides to trap misfit dislocations, we are able to reduce defects that result from lattice mismatch and produce high quality FinFETs.  We are also developing software for the rapid extraction of quantum mechanically corrected C-V parameters for these alternative channel materials with high-k dielectrics.
  • Si CMOS Compatible Optoelectronics: We are investigating methods for improving the photon emission efficiency for Si based quantum dots.  Forming these QDs in a lower bandgap dielectric matrix allows for a higher tunneling probability for electroluminescent devices.  We are also studying the nature of defects within these materials and the means of passivating them for improved device performance.
  • Contact Resistance and Metal Gate Work Function Tuning for Advanced CMOS:  Coming soon. 
  • High Capacity Li-ion Battery Electrodes: Coming soon.