Renaissance Germanium
Lead Research Organisation:
University of Warwick
Department Name: Physics
Abstract
Germanium, in at the birth of the electronics revolution, is experiencing a renaissance as a semiconductor material - possibly even rivalling silicon, and is attracting huge interest as the silicon end-game hots up. It is perceived, audaciously but by many, as a potential candidate to maintain silicon-like technology and associated devices well beyond the envisaged end of silicon development (around 2020) and also take the technology into exciting new areas and performance regimes. This proposal sets out to explore some of the intriguing aspects and consequences of the fundamental electronic structure of Ge not previously examined. There are good theoretical arguments to suggest that some critical performance parameters can be dramatically enhanced if carriers travel in non-conventional crystallographic directions and when the germanium is under strain. We will investigate how these new environments affect the velocity/mobility and effective mass of the carriers (electrons and holes) and the processes that impede their motion (scattering).The project will be conducted by three UK university groups uniquely positioned to undertake this research and with international reputations for epitaxial growth of strained Ge (Warwick), transmission electron microscopy (TEM) for structural characterization on the nanoscale (Sheffield) and carrier transport modelling (Glasgow). The industrial standard CVD growth system at Warwick puts us in a unique position to contribute to this field of research, with good prospects of the high quality Ge structures being available early in the programme. Participation of IMEC, the leading European nano-processing laboratory, will give us unparalleled access to tools not available in the UK. Our intellectual property will be fully protected and could be exploited by numerous companies in the UK.The principal objective is to study 2D carrier transport in these largely untried orientations and to look for significant enhancements in carrier mobility compared to the conventional (100) orientation. Similar investigations are currently underway in silicon and it is opportune to now explore this in Ge. It is particularly timely in the light of IMEC's recent progress in Ge device fabrication using essentially silicon processing techniques.The programme consists of three integrated workpackages:WP1 - Growth and processing of strained Ge channel structures: Epitaxial processes will be developed, structural characterisation performed including high resolution TEM, and simple structures processed for electrical measurement.WP2 - Modulation doped buried channel structures: Initial assessment and screening of orientation and strain influences on hole and electron transport, quickly targeting optimised structures and specifically avoiding any perturbing effects of processing that may be detrimental to electron transport. Results from the measurements will be used by the Glasgow Device Modelling Group to develop/refine basic scattering and mobility models for this materials system and provide pointers to final choice of structures.WP3 - Surface-channel device structures: Structures containing a gate electrode to modulate the carrier population and make it an active device. The gate is separated from the channel by a very thin layer of a new (high-k) dielectric material, which will also scatter the carriers. Transport measurements down to very low temperatures will allow us to appraise the full device potential offered by Ge.By the end of the project we would expect to have a thorough understanding of the practical and theoretical aspects of 2D carrier transport in the full matrix of Ge surface orientations, channel directions and strain. Such knowledge can then be used to great advantage in helping realise new generations of highly performing devices that are needed in the nanoelectronics and the futuristic spintronics era.
People |
ORCID iD |
David Leadley (Principal Investigator) | |
Evan Parker (Co-Investigator) |
Publications
Balestra, Francis
(2010)
Nanoscale CMOS: Innovative Materials, Modeling and Characterization
Balestra, Francis
(2010)
Nanoscale CMOS: Innovative Materials, Modeling and Characterization
Berkutov I
(2012)
On the Magnetoresistance Maximum Observed in the Intermediate Magnetic Field Region for the Two-Dimensional Hole Gas in a Strained Si0.05Ge0.95 Quantum Well
in Journal of Low Temperature Physics
Casteleiro C
(2013)
Thermally grown GeO<inf>2</inf> on epitaxial Ge on Si(001) substrate
Dobbie A
(2012)
Thermal Stability of Thin Compressively Strained Ge Surface Channels Grown on Relaxed Si 0.2 Ge 0.8 Reverse-Graded Buffers
in Journal of The Electrochemical Society
Dobbie A
(2010)
Effect of growth rate on the threading dislocation density in relaxed SiGe buffers grown by reduced pressure chemical vapour deposition at high temperature
in Semiconductor Science and Technology
Dobbie A
(2012)
Ultra-high hole mobility exceeding one million in a strained germanium quantum well
in Applied Physics Letters
Dobbie A
(2012)
Growth of Smooth, Low-Defect Germanium Layers on (111) Silicon via an Intermediate Islanding Process
in Applied Physics Express
Gallacher K
(2012)
Ohmic contacts to n-type germanium with low specific contact resistivity
in Applied Physics Letters
Hassan A
(2013)
Pure Ge quantum well with high hole mobility
Hassan A
(2014)
Anisotropy in the hole mobility measured along the [110] and [1¯10] orientations in a strained Ge quantum well
in Applied Physics Letters
Huy Nguyen V
(2013)
High quality relaxed germanium layers grown on (110) and (111) silicon substrates with reduced stacking fault formation
in Journal of Applied Physics
Leadley D
(2013)
Nanoscale CMOS - Innovative Materials, Modeling and Characterization
Liu X
(2011)
Accuracy of thickness measurement for Ge epilayers grown on SiGe/Ge/Si(100) heterostructure by x-ray diffraction and reflectivity
in Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena
Liu X
(2011)
High-quality Ge/Si 0.4 Ge 0.6 multiple quantum wells for photonic applications: growth by reduced pressure chemical vapour deposition and structural characteristics
in Journal of Physics D: Applied Physics
Mironov O
(2014)
Ultra high hole mobilities in a pure strained Ge quantum well
in Thin Solid Films
Mironov O
(2013)
New RP-CVD grown ultra-high performance selectively B-doped pure-Ge 20 nm QWs on (100)Si as basis material for post-Si CMOS technology
in physica status solidi c
Mironov O
(2015)
Fractional Quantum Hall States in a Ge Quantum Well
Mironov OA
(2016)
Fractional Quantum Hall States in a Ge Quantum Well.
in Physical review letters
Mitard J
(2011)
High Hole Mobility in 65 nm Strained Ge p-Channel Field Effect Transistors with HfO 2 Gate Dielectric
in Japanese Journal of Applied Physics
Myronov M
(2011)
Control of epilayer thickness during epitaxial growth of high Ge content strained Ge/SiGe multilayers by RP-CVD
in Journal of Crystal Growth
Myronov M
(2010)
High Quality Strained Ge Epilayers on a Si[sub 0.2]Ge[sub 0.8]/Ge/Si(100) Global Strain-Tuning Platform
in Electrochemical and Solid-State Letters
Myronov M
(2014)
An extremely high room temperature mobility of two-dimensional holes in a strained Ge quantum well heterostructure grown by reduced pressure chemical vapor deposition
in Japanese Journal of Applied Physics
Nguyen V
(2012)
Epitaxial growth of relaxed germanium layers by reduced pressure chemical vapour deposition on (110) and (111) silicon substrates
in Thin Solid Films
Norris D
(2010)
TEM analysis of Ge-on-Si MOSFET structures with HfO 2 dielectric for high performance PMOS device technology
in Journal of Physics: Conference Series
Norris D
(2010)
TEM analysis of Si-passivated Ge-on-Si MOSFET structures for high performance PMOS device technology
in Journal of Physics: Conference Series
Riddet C
(2012)
Hole Mobility in Germanium as a Function of Substrate and Channel Orientation, Strain, Doping, and Temperature
in IEEE Transactions on Electron Devices
Shah V
(2011)
High quality relaxed Ge layers grown directly on a Si(001) substrate
in Solid-State Electronics
Shah V
(2012)
Reverse graded strain relaxed SiGe buffers for CMOS and optoelectronic integration
in Thin Solid Films
Shah V
(2015)
Electrical properties and strain distribution of Ge suspended structures
in Solid-State Electronics
Shah V
(2013)
Introduction of Terraces into a Reverse Linearly Graded SiGe Buffer on Si(001) Substrate and Their Effect on the Buffer's Structural Properties
in ECS Journal of Solid State Science and Technology
Shah V
(2011)
Effect of layer thickness on structural quality of Ge epilayers grown directly on Si(001)
in Thin Solid Films
Shah V
(2010)
Reverse graded SiGe/Ge/Si buffers for high-composition virtual substrates
in Journal of Applied Physics
Simoen E
(2011)
Low-Frequency Noise Characterization of Strained Germanium pMOSFETs
in IEEE Transactions on Electron Devices
Simoen E
(2011)
Defect-Related Excess Low-Frequency Noise in Ge-on-Si pMOSFETs
in IEEE Electron Device Letters
Zhylik A
(2011)
High-resolution x-ray diffraction investigation of relaxation and dislocations in SiGe layers grown on (001), (011), and (111) Si substrates
in Journal of Applied Physics
Description | Strained germanium layers were grown epitaxially on silicon substrates, with much higher quality than previously achieved, using an industrially compatible technique. The project enabled many advances of the growth technique (RP-CVD) to be explored and world leading material to be produced. Key findings were: (1) The first ever strained Ge MOSFETs were fabricated with 65nm gate lengths on silicon (100) substrates. There is now very considerable interest in Ge as a transitor material, but this was the first invastigation of strained layers with high-k dielectric gates. (2) The highest mobility germanium 2D hole gases were formed, with hole mobility of over 1,000,000 cm^2/Vs, which is an order of magnitude improvement on previous work. This was made possible by the ultra clean growth environment and elimination of impurities in the material. These structures show the fractional quantum Hall effect in Ge for the first time. (3) Growth of relaxed germanium on non-standard orientation silicon substrates (111) and (110) was demonstrated and improved by an order of magnitude in terms of smoothness and threading dislocation density (TDD). The (111) layers were sufficiently smooth for device quality material to be contemplated, which had previously been dismissed as a possibility. |
Exploitation Route | The improved Ge layers could be used as transistor channel material in advanced CMOS processes to give multifold improvements in performance over existing silicon based devices. The very smooth Ge on silicon can act as a substrate for subsequent growth of III-V materials that have particular applications as high efficiency solar cells or as laser sources for communications. The intermediate Ge layers mean that the III-V photonic elements can be more easily integrated with the silicon electronics on a single chip. The improved material could be exploited for consumer applications, as set out below. The ability to grow III-V layers on a silicon substrate could be used by numerous academic groups interested in the properties of the III-Vs. |
Sectors | Digital/Communication/Information Technologies (including Software),Electronics |
Description | Creating silicon based platforms for new technologies |
Amount | £1,680,000 (GBP) |
Funding ID | EP/J001074/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2012 |
End | 02/2017 |
Description | Spintronic device physics in Si/Ge Heterostructures |
Amount | £700,000 (GBP) |
Funding ID | EP/J003263/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 03/2012 |
End | 08/2015 |