5 research outputs found
Raman shifts in MBEâgrown SixGe1âââxâââySny alloys with large Si content
We examine the Raman shift in siliconâgermaniumâtin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, SiâSi, SiâGe, and GeâGe, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1âââxâââySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659Peer Reviewe
Raman shifts in MBEâgrown SixGe1â-âxâ-âySny alloys with large Si content
We examine the Raman shift in silicon-germanium-tin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, Si-Si, Si-Ge, and Ge-Ge, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1â-âxâ-âySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for siliconâbased photonic and microelectronic devices.Deutsche ForschungsgemeinschaftProjekt DEA
Untersuchung von elektrisch aktiven Defekten in Gruppe IV und Gruppe III-N epitaktischen Schichten integriert auf Si Substraten
The hetero-integration of group IV and III-V epitaxial layers on silicon (Si) substrates enables novel devices for optoelectronic and high-power applications. However, lattice and thermal mismachtes lead to an unavoidable formation of defects in hetero-epitaxy. The consideration of these defects is important in semiconductor devices as they affect material properties and impair the device performances. Besides the structural characterization of the unintentional introduced defects and the question of itâs origin, it is essential to evaluate their electrical activity in order to describe their impact on the device performance.
This work explores the electrical activity of threading dislocations (TDs) in Ge-rich SiGe heterostructures integrated on Si substrates as well as the electrical active defects introduced by the growth of aluminium-nitride (AlN) seed layers for the integration of gallium-nitride (GaN) on Si substrates.
I demonstrated a defect-related p-type conductivity of intrinsically grown Si â ÌŁââGe â ÌŁââ/Ge that reaffirms previous work of similar intrinsic Ge-based material. Moreover, I detailed the threading dislocation related leakage currents in rectifying devices, revealing a power law dependence on the threading dislocation density (TDD). By a variation of temperature I determined the dominant mechanism of transport of this leakage currents in different temperature regimes, for which I suggested possible interactions with TD related defect states. Through the reduction of leakage currents in the fabricated MOS capacitors I was able to examine an effective carrier concentration of 5-6x10Âčâ”cmâ»Âł in the nominally intrinsic Si â ÌŁââGe â ÌŁââ epitaxial layer, which decreases down to 1x10Âčâ”cmâ»Âłin the Ge buffer underneath. By applying deep level transient spectroscopy (DLTS) I found one dominant hole trap at mid-gap position confirming the presence of an TD-related effective generation-recombination center. In addition, I investigated the hole trapping kinetics of this defect level and associated it with point defects that are trapped in the strain field around threading dislocations.
I obtained insights into defect formation in the Si substrate and at the AlN/Si interface in dependence of the AlN growth temperature. A low temperature growth step prevented a deep in-diffusion of Al atoms into the Si substrate with simultaneous increase of the maximal p-type doping in the vicinity of the AlN/Si interface. Furthermore, I found a bulk hole trap inside the Si substrate at mid-gap position that showed an increase in density by applying a low temperature growth step. In contrast, the defect states at the AlN/Si interface decreased when a low temperature growth step was applied, in comparison to AlN layers grown at continuous high temperatures.Die Heterointegration von epitaktischen Gruppe IV und Gruppe III-V Schichten auf Silizium (Si) ermöglicht die Herstellung von innovativen Bauelementen fĂŒr optoelektronische- und Hochleistungsanwendungen. Jedoch fĂŒhren Gitterfehlanpassungen und Unterschiede in den WĂ€remausdehnungskoeffizienten zur unvermeidbaren Bildung von Defekten, welche verschiedene Materialeigenschaften beeinflussen und die Funktionsweise der Bauteile beeintrĂ€chtigen. Neben der strukturellen Charakterisierung der Defekte und der Frage nach deren Entstehung, ist es unerlĂ€sslich ihre elektrische AktivitĂ€t zu untersuchen, um den Einfluss auf die Bauteilperformance korrekt beschreiben zu können.
Diese Arbeit untersucht die elektrische AktivitĂ€t von DurchstoĂversetzungen in Silizium-
Germanium (SiGe) Heterostrukturen mit hohem Germanium (Ge) Anteil, gewachsen auf Si Substraten, wie auch die elektrisch aktiven Defekte, welche durch das Wachstum von Alumiunnitrit (AlN) Schichten entstehen, die dazu genutzt werden um Galiumnitrit (GaN) auf Si zu wachsen.
Ich konnte eine defektbedingte p-Dotierung in den undotiert gewachsenen Si â ÌŁââGe â ÌŁââ/Ge Schichten nachweisen. DarĂŒber hinaus habe ich die versetzungsabhĂ€ngigen Leckströme in gleichrichtenden Bauteilen beschrieben, wobei eine PotenzgesetzabhĂ€ngigkeit von der Versetzungsdichte festegellt wurde. Durch eine Variation der Temperatur konnte ich die dominierenden Transportmechanismen der Leckströme bestimmen und habe mögliche Interaktionen mit den versetzungsbedingten DefektbĂ€ndern beschrieben.
Durch das erfolgreiche UnterdrĂŒcken der Leckströme in MOS Kondensatoren bestimmte ich eine effektive LadungstrĂ€gerkonzentration in der intrinsischen Si0.06Ge0.94 Schicht in Höhe von 5-6x10Âčâ”cmâ»Âł. In der darunter liegenden Ge-Pufferschicht sank diese LadungstrĂ€gerkonzentration auf 1x10Âčâ”cmâ»Âł. Mit Hilfe von Transientenspektroskopie tiefer Störstellen (DLTS) bestimmte ich eine löchereinfangende Störstelle in der Mitte der BandlĂŒcke, die ein versetzungs-bedingtes Generation-Rekombinationszentrum in der untersuchten Si â ÌŁââGe â ÌŁââ/Ge Heterostruktur bestĂ€tigte. ZusĂ€tzlich untersuchte ich die Löchereinfangkinetik des gefunden Defektlevels und ordnete es daraufhin Punktdefekten zu, die im Spannungsfeld der DurchstoĂversetzugen lokalisiert sind.
Ich gewann Kenntnisse ĂŒber elektrisch aktive Defekte im Si Substrat und an der AlN/Si GrenzflĂ€che in AbhĂ€ngigkeit der AlN Wachstumstemperatur. Ein Wachstumsschritt bei verringerter Temperatur verhinderte das tiefe Eindringen von Al Atomen in das Si Substrat im Vergleich zum AlN Wachstum bei konstant hoher Temperatur, wohingegen die maximale Dotierung in der NĂ€he der AlN/Si GrenzflĂ€che anstieg. Des Weiteren beobachtete ich ein Defektlevel im Si Subsrtat in der Mitte der BandlĂŒcke. Die Konzentration dieses Defektlevels nimmt zu, wenn der Wachstumsschritt bei verringerter Temperatur durchgefĂŒhrt wird. Im Gegensatz dazu nehmen die Defekte an der AlN/Si GrenzflĂ€che ab
Background Carrier Concentration in Intrinsic Ge-Rich SiGe/Ge Heterostructures Integrated on Si(001)
No abstract available
Raman shifts in MBEâgrown Si x Ge 1 â x â y Sn y alloys with large Si content
We examine the Raman shift in siliconâgermaniumâtin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, SiâSi, SiâGe, and GeâGe, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1âââxâââySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659Peer Reviewe