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Development of new characterization techniques for III-V nanowire devices

Persson, Olof LU (2017)
Abstract (Swedish)
Den här avhandlingen presenterar nya metoder och tekniker som utvecklats för att undersöka nanotrådars (NT) och NT-enheters egenskaper, och de resultat som erhållits med dessa. Växt och karakterisering av NT har blivit en stor forskningsområde då NT har visat sig förbättra egenskaperna hos många tillämpningar inom halvledarteknologin, såsom transistorer, solceller och lysdioder. Strukturell sammansättning, optiska- och elektriska egenskaper hos NT och NT-enheter påverkas av effekter ner på atomär nivå. På grund av det stora ytan/volym-förhållandet hos NT spelar ytan och dess egenskaper, hos NT, en avgörande roll när det gäller att bestämma egenskaperna hos NT. Detta gör karakterisering av dessa strukturer, på atomär nivå, en nyckelfaktor... (More)
Den här avhandlingen presenterar nya metoder och tekniker som utvecklats för att undersöka nanotrådars (NT) och NT-enheters egenskaper, och de resultat som erhållits med dessa. Växt och karakterisering av NT har blivit en stor forskningsområde då NT har visat sig förbättra egenskaperna hos många tillämpningar inom halvledarteknologin, såsom transistorer, solceller och lysdioder. Strukturell sammansättning, optiska- och elektriska egenskaper hos NT och NT-enheter påverkas av effekter ner på atomär nivå. På grund av det stora ytan/volym-förhållandet hos NT spelar ytan och dess egenskaper, hos NT, en avgörande roll när det gäller att bestämma egenskaperna hos NT. Detta gör karakterisering av dessa strukturer, på atomär nivå, en nyckelfaktor för att förstå de bakomliggande mekanismerna, och för att utvecklingen av bättre strukturer.
I den här avhandlingen är sammansättningen hos III-V halvledarmaterial och de elektroniska egenskaperna hos III-V NT undersökta med hjälp av svepspetsmikroskopi (SSM) och fotoelektronspektroskopi (FES).
En ny metod för att studera kontaktade NT på isolerande substrat med SSM beskrivs, och resultaten från undersökningar av InAs-GaSb Esaki-diod-NT presenteras. Möjligheten att studera sidofasetter av NT med SSM samtidigt som en potential ligger över NT gör det möjligt att korrelera diodens prestanda med NTs egenskaper.
Konduktiviteten hos stående NT mäts också med SSM med en ny metod som kallas toppkontakt läge. Metoden används för att utvärdera den Schottky-barriär Au-GaAs-gränssnittet i GaAs-NT och ledningsförmågan hos InP- och InAs-NT. Metoden gör det möjligt att mäta den elektriska ledningsförmågan hos NT utan ytterligare processering, vilket gör det till en mer tillförlitlig metod pga de bra ohmska elektriska kontakterna till NT. Toppkontakt läge möjliggör också, till skillnad från konventionella metoder, välkontrollerad ytbehandling av sidofasetter hos NT vilket kan används för att visa hur ytoxider påverka NTs konduktans.
FES och mer genomträngande hårdröntgenfotoelektronspektroskopi (HÅRFES) används för att utvärdera homogeniteten och tillväxten av HfO2-filmer på InAs. Även mekanismerna bakom den självrengörande effekten av den naturliga InAs-oxiden undersöks. Information är särskilt viktigt för det fortsatta arbetet med halvledartransistorer där HfO2 är en av de bästa kandidaterna som styreoxid. Gränssnittet mellan oxid och halvledare är avgörande för enhetens prestanda.
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Abstract
This dissertation presents the new methods and techniques developed to investigate the properties of nanowires (NWs) and NW devices and the results obtained using these methods. The growth and characterization of NWs have become a large research field because NWs have been shown to improve the properties of many semiconductor applications such as transistors, solar cells, and light emitting diodes. The structural composition, optical properties, and electric characteristics of NWs and NW devices are affected by effects at the atomic level. The surface of NWs plays a crucial role when it comes to these characteristics because of the large surface to volume ration of the NW structures. This makes the characterization of these structures, at... (More)
This dissertation presents the new methods and techniques developed to investigate the properties of nanowires (NWs) and NW devices and the results obtained using these methods. The growth and characterization of NWs have become a large research field because NWs have been shown to improve the properties of many semiconductor applications such as transistors, solar cells, and light emitting diodes. The structural composition, optical properties, and electric characteristics of NWs and NW devices are affected by effects at the atomic level. The surface of NWs plays a crucial role when it comes to these characteristics because of the large surface to volume ration of the NW structures. This makes the characterization of these structures, at the atomic level, a key factor, for understanding the underlying mechanisms, and for the development of even more suitable structures. Here, the composition of III-V semiconductor materials and the electronic properties of III-V semiconductor NWs are investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS).
A new method for studying contacted NWs on insulating substrates with STM is described, and the results from investigations of InAs-GaSb Esaki diode NWs are presented. The ability to study the NW side facets with STM while at the same time being able to apply a potential along the NW makes it possible to connect the device performance with the NW characteristics found with the STM.
The conductivity of up-standing, as grown NWs is also measured with an STM using the novel technique called top contact mode. The method is used to evaluate, the Schottky barrier height of the Au GaAs interface in GaAs NWs, and the conductivity of InP and InAs NWs. This method makes it possible to measure the electric conductivity of the NWs without any additional device fabrication, making it more reliable due to the good ohmic electrical contacts established to the NW. It also, in contrast to conventional methods, enables well-controlled surface treatment of the NW side facets which is used to show how surface oxides influence NW conductance.
XPS and the more penetrating hard X-ray photoelectron spectroscopy (HAXPES) are used to evaluate the homogeneity and the growth of HfO2 films on InAs as well as the mechanism behind the self-cleaning effect of the InAs native oxide. This information is especially important for the continued work on semiconductor transistors where the HfO2 is one of the best candidates to be used as the gate oxide and where the interface between the oxide and semiconductor is crucial for device performance.
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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof. Talin, A. Alec, Sandia National Laboratories, Livermore, CA, USA
organization
alternative title
Development of new characterization techniques for III-V nanowire devices
publishing date
type
Thesis
publication status
published
subject
keywords
STM, XPS, Semiconductor nanowires, nanowire devices, top contact mode, HAXPES, Fysicumarkivet A:2017:Persson
pages
214 pages
publisher
Lund University, Faculty of Science, Department of Physics, Division of Synchrotron Radiation Research
defense location
Rydberg lecture hall, Department of Physics, Sölvegatan 14A, Lund
defense date
2017-02-03 09:15
ISBN
978-91-7753-128-9
978-91-7753-129-6
language
English
LU publication?
yes
id
a49d3dc1-7c2c-481c-8002-e2236bfa7340
date added to LUP
2017-01-04 11:45:12
date last changed
2017-01-25 14:27:21
@phdthesis{a49d3dc1-7c2c-481c-8002-e2236bfa7340,
  abstract     = {This dissertation presents the new methods and techniques developed to investigate the properties of nanowires (NWs) and NW devices and the results obtained using these methods. The growth and characterization of NWs have become a large research field because NWs have been shown to improve the properties of many semiconductor applications such as transistors, solar cells, and light emitting diodes. The structural composition, optical properties, and electric characteristics of NWs and NW devices are affected by effects at the atomic level. The surface of NWs plays a crucial role when it comes to these characteristics because of the large surface to volume ration of the NW structures. This makes the characterization of these structures, at the atomic level, a key factor, for understanding the underlying mechanisms, and for the development of even more suitable structures. Here, the composition of III-V semiconductor materials and the electronic properties of III-V semiconductor NWs are investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). <br/>A new method for studying contacted NWs on insulating substrates with STM is described, and the results from investigations of InAs-GaSb Esaki diode NWs are presented. The ability to study the NW side facets with STM while at the same time being able to apply a potential along the NW makes it possible to connect the device performance with the NW characteristics found with the STM.  <br/>The conductivity of up-standing, as grown NWs is also measured with an STM using the novel technique called top contact mode. The method is used to evaluate, the Schottky barrier height of the Au GaAs interface in GaAs NWs, and the conductivity of InP and InAs NWs. This method makes it possible to measure the electric conductivity of the NWs without any additional device fabrication, making it more reliable due to the good ohmic electrical contacts established to the NW. It also, in contrast to conventional methods, enables well-controlled surface treatment of the NW side facets which is used to show how surface oxides influence NW conductance.<br/>XPS and the more penetrating hard X-ray photoelectron spectroscopy (HAXPES) are used to evaluate the homogeneity and the growth of HfO2 films on InAs as well as the mechanism behind the self-cleaning effect of the InAs native oxide. This information is especially important for the continued work on semiconductor transistors where the HfO2 is one of the best candidates to be used as the gate oxide and where the interface between the oxide and semiconductor is crucial for device performance.<br/>},
  author       = {Persson, Olof},
  isbn         = {978-91-7753-128-9},
  keyword      = {STM,XPS,Semiconductor nanowires,nanowire devices,top contact mode,HAXPES,Fysicumarkivet A:2017:Persson},
  language     = {eng},
  pages        = {214},
  publisher    = {Lund University, Faculty of Science, Department of Physics, Division of Synchrotron Radiation Research},
  school       = {Lund University},
  title        = {Development of new characterization techniques for III-V nanowire devices},
  year         = {2017},
}