Accomplishment

2019

• Evidence for exchange Dirac gap in magneto-transport of topological insulator-magnetic insulator hetero-structures
• Low-Temperature Ultra-Thin Epitaxial Si Cap Enabling Highly Reliable Ge MOS
• Thin single crystal Si-capped Ge(100), (110), and (111) Gate Stacks - Attainment of Low Interfacial Trap Density for FinFET Application and the Reliability. [very low Dit around 1E11 eV-1cm-2 with a minimum value of ~6.0 E10 eV-1 cm-2 in the Si-capped Ge(110)]
• Atom-to-atom interaction of atomic O with epi Ge(001)-2×1 in elucidating GeOx formation
• Molecular beam epitaxy, atomic layer deposition, and multiple functions connected via ultra-high vacuum

2018

• Topological insulator Bi2Se3 films on rare earth iron garnets and their high-quality interfaces with a novel growth [This paper was selected as Featured in Appl. Phys. Lett. 114 (2019)]
• Atom-to-atom interaction of O2 with epi Ge(001)-2×1 in elucidating GeOx formation
• High-quality thulium iron garnet films with tunable perpendicular magnetic anisotropy by off-axis sputtering - correlation between magnetic properties and film strain
• Atomic nature of the growth mechanism of atomic layer deposited high‑κ Y2O3 on GaAs(001)‑4 × 6 based on in situ synchrotron radiation photoelectron spectroscopy

2017

• Strongly exchange-coupled and surface-state-modulated magnetization dynamics in Bi2Se3/YIG hetero-structures
• Enhancement of dielectric constant using high-temperature mixed and sub-nano-laminated atomic layer deposited Y2O3/Al2O3 on GaAs(001)
• Van der Waals epitaxy of topological insulator Bi2Se3 on single layer transition metal dichalcogenide MoS2

2016

• Single-crystal single-domain hexagonal perovskite YAlO3 epitaxially on GaAs(111)A using nano-laminated atomic-layer-deposited (ALD) Y2O3(2.03 nm)/Al2O3(1.08 nm) multilayers
• Demonstration of large field effect in topological insulator films via a high-k dielectric as the back gate
• Attainment of Schottky barrier height of 0.38 eV and Ag(+)-As(-) dipole potential energy of 0.26 eV at deposition of Ag 0.25 Å thick on GaAs(001) prior to the observation of metallic behavior of Ag!

2015

• Achieving record high extrinsic drain current >1.8 mA/mm and transconductance >0.95 mS/mm in 1mm gate length in self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors with in-situ deposited ALD-Al2O3 as gate dielectrics
• Self-aligned inversion-channel n-InGaAs, p-GaSb, and p-Ge MOSFETs with a common high k gate dielectric using a CMOS compatible process
• Single-crystal Y2O3 epitaxially on GaAs(001) and (111) using atomic layer deposition with extremely small frequency dispersion at accumulation in the CV curves and interfacial trap density in 2-4 E11 cm-2eV-1 using conductance method

2014

• Greatly improved interfacial passivation of in-situ high dielectric deposition on freshly grown molecule beam epitaxy Ge epitaxial layer on Ge(100)
• Observation of Strongly Enhanced Inverse Spin Hall Voltage in Fe3Si/GaAs Structures

2013

• Achieving record high drain current >1.5 mA/mm and transconductance >1.0 mS/mm in 1mm gate length self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors with in-situ deposited ALD-HfO2 as gate dielectrics
• Effectively passivating GaSb with UHV-deposited and ALD-Y2O3, achieving very low interfacial trap densities and record-high drain currents in self-aligned inversion-channel GaSb MOSFETs

2012

• Both ALD- and MBE-HfO2 based high-κ dielectrics on In0.53Ga0.47As and In0.2Ga0.8As with low Dit's, excellent thermodynamic stability, and outstanding oxide scalability, thus breaking the myth that tetravalent oxides such as HfO2 could not give an excellent high-κ/InGaAs interface
• First to probe atom-to-atom interactions for atomic layer deposition of trimethylaluminum/H2O on Ga-rich GaAs(001)- 4x6 and As-rich GaAs(001)-2x4 surfaces using in-situ synchrotron-radiation photoemission

2011

• Achieving record high drain current >1.5 mA/mm in self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors with in-situ deposited Al2O3/Y2O3 as gate dielectrics
• Direct determination of flat-band voltage for metal/high k oxide/semiconductor heterointerfaces by electric-field- induced second-harmonic generation
• Achieving a record-low interfacial density of states with a flat distribution in Ga2O3(Gd2O3) directly deposited on Ge
• Atomic-scale determination of band offsets at Gd2O3/GaAs (100) hetero-interface using scanning tunneling spectroscopy type

2010

• Attainment of low interfacial trap density absent of a large mid-gap peak in In0.2Ga0.8As by Ga2O3(Gd2O3) passivation
• In-situ ALD Al2O3 on GaAs - achieving more symmetrical CVs, unparalleled by comparing with other ALD approaches, which give good CVs for p-type, but poor for n-type
• In-situ synchrotron photoemission studies on high k's on GaAs and Ge in attaining detailed interfacial atomic/ chemical bonding
• Effective reduction of interfacial traps in Al2O3/GaAs (001) gate stacks using surface engineering and thermal annealing

2009

• Achieving drain current enhancement and negligible current collapse in GaN metal-oxide-semiconductor field-effect-transistor with aid of high-quality ALD-oxides/GaN interface.
• Achieving nanometer-thick 0.5 nm CET single-crystal hexagonal Gd2O3 on GaN with exceptional high-temperature thermal stability (1100 °C) for advanced complementary metal-oxide-semiconductor technology
• Achieving nanometer-thick 0.6 nm CET amorphous/single-crystal Ga2O3(Gd2O3) on InGaAs with exceptional high-temperature thermal stability (900 °C) for advanced complementary metal-oxide-semiconductor technology
• Achieving Ga2O3(Gd2O3) on Ge without interfacial layers and also a low EOT of 0.6 nm

2008

• First to achieve an EOT of 1.0 nm in both MBE and ALD oxide deposited on InGaAs
• Achieving low interfacial trap density in atomic layer deposited (ALD) Al2O3 on In0.53Ga0.47As
• Single crystal GaN on Si with nm-thick single crystal Sc2O3 and Al2O3 as a template
• UHV high k dielectrics of Ga2O3(Gd2O3), HfO2, and Y2O3 on Ge without interfacial layers - achieving excellent electrical properties

2007

• First to demonstrate a self-aligned inversion-channel Ga2O3(Gd2O3)/InGaAs MOSFET with world-record device performance in terms of drain currents of > 1mA/mm and transconductance of > 0.7 mS/mm in a 1 mm gate length device
• First to achieve true inversion-channel GaN metal-oxide-semiconductor field-effect transistor with atomic-layer- deposited Al2O3 as gate dielectric
• First self-aligned inversion n-channel InGaAs/GaAs metal-oxide-semiconductor field-effect-transistors with TiN gate and Ga2O3(Gd2O3) dielectric
• First to use atomic-layer-deposited (ALD) HfO2 on In0.53Ga0.47As: passivation and energy-band parameters

2006

• Cubic HfO2 doped with Y2O3 epitaxial films on GaAs (001) of enhanced dielectric constant of 34
• First to determine energy-band parameters of atomic-layer-deposition-Al2O3/InGaAs heterostructures

2005

• First to understand the mechanism of Fermi-level unpinning in ALD grown Al2O3 on InGaAs
• A novel approach of using a molecular beam epitaxy grown template for subsequent atomic layer deposition of high k dielectrics on Si without any interfacial layer to achieve a very low EOT
• Growth of perfected nano-thick single crystal oxide films (gamma Al2O3 and Sc2O3) on Si

2004

• First to achieve high-temperature thermodynamic stability and low interfacial density of states in Ga2O3 (Gd2O3)/GaAs interface - a must for self-aligned inversion-channel InGaAs MOSFET's
• First to grow all single-crystal heterostructures in GaN/Rare Earth Oxides (Gd2O3, Y2O3)/GaN with sharp interfaces and a low interfacial density of states in each interface

2003

• Fabrication of GaAs MOSFET with oxide gate dielectric grown by atomic layer deposition (ALD)

2002

• First to grow an all single crystal heterostructure in GaN/Rare Earth Oxides (Gd2O3, Y2O3)/GaN with sharp interfaces and a low interfacial density of states in each interface (opening up a possibility of building three-dimensional integrate circuits)
• Direct atomic structure determination of epitaxially grown films: Gd2O3 on GaAs (100)

2001

• First to achieve a chemically abrupt, atomically sharp oxide/Si interface with a low interracial density of states using an e-beam/UHV (MBE) approach (a very significant accomplishment in microelectronics in replacing SiO2 with high-k gate dielectrics)

2000

• First to demonstrate a GaAs CMOS inverter
• First to grow hcp single crystal rare earth oxides (a high temperature phase) on GaN with a low interfacial density of states
• First to grow a new fcc Gd2O3 phase on GaAs

1999

• New high e (dielectric constant) gate dielectrics Gd2O3 and Y2O3 for Si. Using ultrahigh vacuum vapor deposition, for instance, amorphous Y2O3 films 45 Å thick (with a e ~ 18-19) showed a remarkably low leakage current of 1E-6 ~1E-7 A/cm2 at 1V for a teq of only 10 Å. This data is, at least, 5 orders of magnitude better than the best SiO2 gate dielectric 15 Å thick.
• Demonstrated a low interfacial density of states in MOS diodes of (Ga,Gd)2O3 and SiO2 on GaN using ultrahigh vacuum vapor deposition.
• First to demonstrate a GaN MOSFET operated at 400°C.
• Fabricated GaAs power MOSFETs with a gate periphery up to 2 cm, under a 5V drain bias showing maximum output power of 26.5 dBm and peak power added efficiency (PAE) of 56%.
• Fabricated sub-micron depletion-mode GaAs MOSFET's (0.8 x 60 mm^2). First such devices exhibit negligible drain current drift and hysteresis, and show a drain current density of 450 mA/mm, a transconductance of 130 mS/mm, a fT of 17 GHz, and a fmax of 60 GHz. These excellent device characteristics show a significant advance towards the manufacture of commercially useful GaAs MOSFET's.

1998

• First to demonstrate depletion-mode GaAs MOSFET's with accumulation mode up to +3V or higher. For the first time, the D-mode GaAs MOSFET's exhibiting negligible drain current drift and hysteresis.
• First to grow a single-domain single-crystal Gd2O3 (a Mn2O3 structure) epitaxially on GaAs with a low interfacial density of states (Dit).
• First to observe single-domain single-crystal epitaxial growth of (Ga,Gd)2O3 on GaAs for the first few mono-layers. The probing using XPS shows very little Ga, indicating that the epitaxial growth of the first few mono-layers of Gd2O3 on GaAs may be responsible for the low Dit.
• Greatly improve drain current to 3 mA (from 10-20 mA in the 1996 device) in enhancement-mode GaAs MOSFET.

1997

• First to demonstrate enhancement-mode InGaAs MOSFETs with inversion on semi-insulating InP substrates. For the first time, no drain-current drifting or hysteresis was observed in the enhancement-mode InGaAs MOSFET's.

1996

• First to demonstrate enhancement-mode n- and p-channel GaAs MOSFETs with inversion. This will open up applications (both analog and digital) in low-power, high speed/frequency components and systems.

1995

• For the first time, the formation of inversion layers in both n- and p-type GaAs has been clearly demonstrated. This was made possible by a discovery of a novel oxide of (Ga,Gd)2O3, which gives the oxide-GaAs heterostructues of a low interfacial density of states in mid 1E10 cm^-2 eV^-1 range and an interface recombination velocity of 4500 cm/sec.The interfaces are thermodynamically and photo-chemically stable.
• Developed an in-situ cleavage tool in MBE chamber to cleave laser bars and subsequently to in-situ deposit oxides on laser facets to prolong the laser lifetime.

1994

• Fabricated record low total electrical resistivity vertical cavity surface emitting lasers.
• Fabricated surface emitting lasers with DBR mirrors of GaAs/AlGaAs and InGaP/GaAs/InGaAs active region with the DBR grown by MBE and the active region grown by MOVPE.
• Developed materials for high-temperature (650C) non-alloyed ohmic contacts for GaAs based materials.

1993

• Fabricated and demonstrated the operation of vertical cavity zone lasers. This new class of high power (>100 mW) high efficiency (>36 %) large area (70 mm in diameter) SELs have an output that is automatically focused to a spot at a particular distance away from the laser.
• Fabricated extremely low electrical resistivity non-alloyed ohmic contacts to both p- and n-GaAs, which have an atomically smooth and chemically abrupt metal-semiconductor interface.
• Demonstration of an isolated buried channel field-effect transistor fabricated via in situ patterned electron-beam deposition of Si in GaAs.

1992

• Demonstrated the first CW buried AlGaAs/GaAs/InGaAs laser diode in both edge emitting and vertical cavity surface emitting configurations using in-situ electron cyclotron resonance (ECR) anisotropic etch and molecular beam epitaxial regrowth.
• Demonstrated a complete removal of GaAs surface contaminants using ECR hydrogen plasma treatment followed by chemical chlorine etching.
• Demonstrated a design optimization for high-power and high-speed surface emitting lasers.

1991

• Growth of vertical cavity surface emitting laser (SEL) to demonstrate ultrafast (up to 39 GHz) relaxation oscillation.
• Electron cyclotron resonance plasma processing of air-exposed AlGaAs (up to 100 at% Al) and AlGaAs regrowth by molecular beam epitaxy (MBE).
• Demonstrated the longest wavelength QWIP ever measured with a cutoff wavelength of lc=14.9 mm.

1990

• Proposed and demonstrated for the first time a novel edge-emitting periodic index separate confinement heterostructure (PINSCH) semiconductor quantum well laser.
• Developed a new cell temperature modulation MBE technique (without shutter operation) to grow any multi-layers with continuously graded interfaces to greatly reduce the series resistance and applied this new technique to the growth of vertical cavity SEL and PINSCH lasers. (This is a very simple technique yet an important technology, which is now being applied to and commonly used in the MOCVD growth of low-resistivity SEL.)
• Introduced hybrid thin metal (<300 Å)/semiconductor mirrors for vertical-cavity surface emitting lasers to emit light from the top.
• Growth of a new intermetallic compound Fe3(Al,Si) films epitaxially on GaAs in which one mono-layer was found to be atomically smooth.

1989

• Developed and set up a multi-chamber MBE system consisting of solid-source III-V compound semiconductor, metal, and an ECR etching chamber (the first cluster tool).

1988

• First to report single-phase high Tc Tl2Ba2Ca2Cu3O10 films carrying high Jc of 10^5 A/cm^2 at 100K.
• Contributed to in-situ epitaxial growth of YBa2Cu3O7 films by MBE with an activated oxygen source.

1987

• Reported the first growth of YBa2Cu3O7-x films by sputtering with Tc over 77K.

1986

• Contributed to the first discovery of magnetic interlayer exchange coupling in rare-earth superlattices of Gd-Y, Gd-Dy, Ho-Y, and Dy-Y, including the first attainment of the anti-ferromagnetic coupling through non-magnetic media which is the foundation for the later discovery of giant magneto-resistance (GMR).

1985

• Contributed to the first successful growth of magnetic superlattices by metal MBE.

1983-84

• First to report the microstructural dependence of magnetic anisotropic properties and aging of amorphous rare-earth transition metal films, which are used as media for magneto-optical recording.

1982

• Used the concept of Ta doping and Jc vs microstructure to greatly enhance the liquid-infiltration processed Nb-Sn wires to carry 10^5 A/cm^2 at 20T and 4.2K.

1981

• Designed a novel heat treatment to optimize the microstructure in the bronze-processed Nb-Sn wires for carrying higher Jc at high magnetic fields.

1979-80

• Developed direct sod state precipitation technique to fabricate ductile superconducting A15 wires in the V-Ga and Nb-Al systems.