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Electrical Studies of Quantum Devices

Carlsson, Sven-Bertil (1999)
Abstract (Swedish)
Popular Abstract in Swedish

Denna avhandling behandlar studier av elektriska komponenter med egenskaper dominerade av s.k. kvantfenomen. Dessa komponenter har ur flera synvinklar många önskvärda egenskaper, t.ex. är vissa av dem extremt snabba, andra har mycket låg effektförbrukning eller hög packningstäthet. Avhandlingen är indelad i två delar. Först en introduktion till ämnet där bakomliggande teori och mätmetoderna beskrivs samt 7 st. vetenskapliga artiklar som i detalj beskriver resultaten. Tre typer av komponenter har studerats och dessa är resonant tunnling, kvantiserad konduktans och en-elektron effekter.



Resonant tunnling uppkommer i ett prov där strömmen tvingas passerar ett område där bara vissa... (More)
Popular Abstract in Swedish

Denna avhandling behandlar studier av elektriska komponenter med egenskaper dominerade av s.k. kvantfenomen. Dessa komponenter har ur flera synvinklar många önskvärda egenskaper, t.ex. är vissa av dem extremt snabba, andra har mycket låg effektförbrukning eller hög packningstäthet. Avhandlingen är indelad i två delar. Först en introduktion till ämnet där bakomliggande teori och mätmetoderna beskrivs samt 7 st. vetenskapliga artiklar som i detalj beskriver resultaten. Tre typer av komponenter har studerats och dessa är resonant tunnling, kvantiserad konduktans och en-elektron effekter.



Resonant tunnling uppkommer i ett prov där strömmen tvingas passerar ett område där bara vissa energinivåer är tillåtna. Endast elektroner med "rätt" energi kan passera och denna energi bestäms av den pålagda spänningen. Detta får till följd att strömmen ökar när spänningen närmar sig resonans värdet och därefter minskar igen även om spänningen fortsätter öka. Denna effekt kan användas för att tillverka kretsar som fungerar vid extremt höga frekvenser och som minskar antalet komponenter som behövs för att bygga vissa kretsar.



Kvantiserad konduktans säger att konduktansen, d.v.s. det motstånd elektroner känner, i extremt små komponenter bara kan anta vissa speciella värden, att jämföra med en "vanlig" komponent där konduktansen kan anta vilket värde som helst. Elektroner kan beskrivas med både våg och partikel egenskare och när dimensionerna blir tillräckligt små gör sig vågegenskaperna tillkänna. För mycket smala kanaler kan bara elektroner som har en våglängd som passar kanalens dimensioner passera. Om vi mäter konduktansen medan vi gör kanalen smalare kommer alltså det motstånd elektronerna känner, d.v.s. konduktansen, förändras i steg varje gång en ny multipel av denna våglängd passar.



En-elektron fenomen bygger på att negativt laddade partiklar repellerar varandra. Denna effekt kan användas till att kontrollera flödet av enskilda elektroner om strömmen i en krets tvingas passera en metallisk ö. Om en elektron befinner sig på ön kan inte ytterliggare en komma dit p.g.a. tidigare nämnda repulsion. Först när elektronen på ön har fortsatt genom kretsen kan nästa elektron äntra ön osv. Med en extern spänning kan man sedan styra om det är tillåtet att passera ön. d.v.s. man kan slå på respektive av strömmen precis som i en vanlig transistor. Då elektronerna passerar ön en och en kallas kretsen "en-elektron transistorn". En-elektron transistoren kan användas i t.ex. framtida minneskretsar som då kan göras mycket energisnåla eller för att göra en extremt noggran strömmätare. (Less)
Abstract
This thesis deals with electrical measurements on quantum devices. The thesis is divided into three major areas: electrical characterization, semiconductor devices, and metal devices.



The electrical characterization part present problems and advantages with the measurement techniques used in the the thesis, .i.e., Current-Voltage; Conductance, including higher order harmonics; Capacitance; Cross-capacitance compensation; and In situ measurements.



The work done in semiconductor materials includes measurements of the Schottky properties for Au on InP, which were shown to improve by growing a top layer of GaInP before depositing the Au. The technique was used to fabricate a HEMT transistor. Schottky... (More)
This thesis deals with electrical measurements on quantum devices. The thesis is divided into three major areas: electrical characterization, semiconductor devices, and metal devices.



The electrical characterization part present problems and advantages with the measurement techniques used in the the thesis, .i.e., Current-Voltage; Conductance, including higher order harmonics; Capacitance; Cross-capacitance compensation; and In situ measurements.



The work done in semiconductor materials includes measurements of the Schottky properties for Au on InP, which were shown to improve by growing a top layer of GaInP before depositing the Au. The technique was used to fabricate a HEMT transistor. Schottky diodes with buried nm-sized metal particles were investigated for different particle densities and sizes and the theory for nanoscopic exclusions was found to agree with experimental data. Resonant tunneling diodes were fabricated in GaInP/GaAs materials. Negative differential resistance was observed with a peak-to-valley ratio of 5.9.



In metals the combination of in situ measurements and the ability to move nm-sized particles with the tip of an atomic force microscope have shown quantized conductance at room temperature which could be tuned to predetermined values and it was stable for hours on individual plateaus. This technique also gave the possibility to tune the width of the tunneling gaps with Ångström control. The tuning technique was employed to fabricate Single-Electron Transistors (SETs) with a charging energy of 4.5 meV. Gate oscillations were observed for these devices up to 25 K. The theoretical charging diagram for a double dot Coulomb blockade device was experimentally verified. The technique allows for making very asymmetric SETs and the Coulomb staircase for both single and double dot SETs has been investigated. The asymmetry in a SET can be used for rectifing purposes and a so-called Coulomb blockade ratchet was shown to rectify an ac signal where the induced dc current direction could be controlled by the gate voltage. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof Paalanen, Mikko, Helsinki University of Technology
publishing date
type
Thesis
publication status
published
subject
keywords
Single electron transistor, Resonant tunneling diode, Quantized conductance, In situ measurements, Coulomb blockade Ratchet, Fysicumarkivet A:1999:Carlsson, Fysik, Physics
pages
116 pages
publisher
Solid State Physics, Lund University
defense location
Physics department Hall B
defense date
1999-12-03 13:15
external identifiers
  • Other:ISRN: LUFTD2/TFFF--99/1056--SE
ISBN
91-628-3817-2
language
English
LU publication?
no
id
e9ae1fde-7b91-4b02-82a6-df55d7c18454 (old id 40116)
date added to LUP
2007-06-20 12:18:40
date last changed
2016-09-19 08:45:15
@misc{e9ae1fde-7b91-4b02-82a6-df55d7c18454,
  abstract     = {This thesis deals with electrical measurements on quantum devices. The thesis is divided into three major areas: electrical characterization, semiconductor devices, and metal devices.<br/><br>
<br/><br>
The electrical characterization part present problems and advantages with the measurement techniques used in the the thesis, .i.e., Current-Voltage; Conductance, including higher order harmonics; Capacitance; Cross-capacitance compensation; and In situ measurements.<br/><br>
<br/><br>
The work done in semiconductor materials includes measurements of the Schottky properties for Au on InP, which were shown to improve by growing a top layer of GaInP before depositing the Au. The technique was used to fabricate a HEMT transistor. Schottky diodes with buried nm-sized metal particles were investigated for different particle densities and sizes and the theory for nanoscopic exclusions was found to agree with experimental data. Resonant tunneling diodes were fabricated in GaInP/GaAs materials. Negative differential resistance was observed with a peak-to-valley ratio of 5.9.<br/><br>
<br/><br>
In metals the combination of in situ measurements and the ability to move nm-sized particles with the tip of an atomic force microscope have shown quantized conductance at room temperature which could be tuned to predetermined values and it was stable for hours on individual plateaus. This technique also gave the possibility to tune the width of the tunneling gaps with Ångström control. The tuning technique was employed to fabricate Single-Electron Transistors (SETs) with a charging energy of 4.5 meV. Gate oscillations were observed for these devices up to 25 K. The theoretical charging diagram for a double dot Coulomb blockade device was experimentally verified. The technique allows for making very asymmetric SETs and the Coulomb staircase for both single and double dot SETs has been investigated. The asymmetry in a SET can be used for rectifing purposes and a so-called Coulomb blockade ratchet was shown to rectify an ac signal where the induced dc current direction could be controlled by the gate voltage.},
  author       = {Carlsson, Sven-Bertil},
  isbn         = {91-628-3817-2},
  keyword      = {Single electron transistor,Resonant tunneling diode,Quantized conductance,In situ measurements,Coulomb blockade Ratchet,Fysicumarkivet A:1999:Carlsson,Fysik,Physics},
  language     = {eng},
  pages        = {116},
  publisher    = {ARRAY(0xb671798)},
  title        = {Electrical Studies of Quantum Devices},
  year         = {1999},
}