1. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Quantum barrier devices
for sub-millimetre wave detection
October 2015 Viktor Doychinov

2. Presentation Contents
• Introduction
• Aim of project
• Rationale for Resonant-Tunnelling Diode use
• Sub-harmonic mixers
• Amplifiers
• Waveguide components
• Summary
Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING

3. Overall project aim
A parametric design study to investigate the applicability
of resonant-tunnelling diodes as non-linear element
in sub-harmonic mixer and amplifier circuits
at millimetre-wave and sub-millimetre wave frequencies,
and to determine desired device characteristics
Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING

4. Resonant-Tunnelling Diodes (RTD)
• Current-voltage characteristic – potential advantages
• I-V regions and applications
• Layer engineering benefits
Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING

5. Resonant-Tunnelling Diodes at the University of Leeds
Layer details
Name Barrier width [nm] Barrier material Well width [nm] Well material
L938 5 Al0.4Ga0.6As 5 GaAs
L939 1.7 AlAs 5 GaAs
L940 5 Al0.4Ga0.6As 5 GaAs
Size details
Parameter Size 1 (D1) Size 2 (D2) Size 3 (D3) Size 4 (D4) Size 5 (D5)
Width [µm] 5 5 5 5 5
Length [µm] 6 12 22 45 90
Area [µm2] 30 60 110 225 450
Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING

6. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
RTD Model Used in Circuit Simulator

7. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Sub-Harmonic Mixer Circuits
• Properties
• Typical topology
• Role of transmission line stubs
• Harmonic used
• Applications

8. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Circuits designed
• Substrates and technology used
• Coplanar Waveguide
• Duroid RT6010 – three variants
• Duroid RO4350B
• Quartz
• Frequency bands – main
• RF = 20 GHz, LO = 9 GHz
• RF = 100 GHz, LO = 49 GHz
• LO harmonic number
• Both n=2 and n=4 mixers

9. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Device scaling – higher frequencies
• Device scaling
• Purpose
• Types – capacitance, capacitance and I-V
• Frequency bands
• RF = 100 GHz, LO = 24 GHz
• RF = 424 GHz, LO = 100 GHz
• 4th Harmonic mixers

10. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Summary of obtained results
• Conversion loss – best performance around 20 dB
• Semiconductor layer effect – L938/L940 close to identical, L939 better
performance, higher power requirement
• Device size effect – Existence of optimal size, trade-off Cj0 vs current
density
• Harmonic number effect – at least 10 dB increase in CL
• Device scaling effect – full scaling improves CL by up to 10 dB

11. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Amplifier Circuits
• Motivation
• Stand-alone amplifier
• Mixer complement
• Types investigated
• Reflection based amplifier
• Active transmission line

12. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Reflection based amplifier
• Schematic and principle of operation
• Key component – coupler
• Designed circuits – 20 GHz, 100 GHz
• Challenges – coupler, RF Choke
• Substrates – Duroid RT6010, Quartz
• Technology – CPWG

13. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Reflection based amplifier – summary of results
• Predicted gain – up to 10 dB at 20 GHz, or 5 dB at 100 GHz with
S11 < 0 dB; overall narrow-band amplification behaviour
• Semiconductor layer effect – no definitive pattern, individual NDR
shapes and characteristics more important
• Device size effect – smaller devices perform better, due to
smaller Cj0

14. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Active transmission line
• Core idea and principle
• Design types – Single bias,
Double bias
• Differences in approach

15. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Active transmission line – summary of results
• Maximum frequency – line acts as low-pass filter
• Flat stable gain – low, on the order of 3 dB
• Resonant gain – high, 10 dB or more
• Design type comparison

16. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Device scaling for amplifier circuits
• Effect on reflection based amplifiers
• Full scaling leads to better performance
• Larger devices now viable
• No overall increase in maximum gain
• Effect on active transmission lines
• Tremendous increase of maximum frequency – up to 650 GHz
• No effect of I-V scaling, capacitance main factor
• Resonant gain of 10 dB at sub-millimetre wave frequencies

17. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Waveguide Couplers
• Motivation
• Coupler type – single aperture narrow
wall
• Principle of operation
• Designs
• Block fabrication and challenges

18. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Overall Conclusions
• Use of RTDs in sub-harmonic mixer circuits
• Use of RTDs in amplifier circuits
• Device scaling and predicted effects
• Waveguide technology capabilities
• Future work

19. Institute of Microwaves and Photonics
SCHOOL OF ELECTRONIC AND ELECTRICAL ENGINEERING
Thank you for your attention!