Struktur innerer Grenzflächen von (GaIn)(NAs)-Heterostrukturen und Eigenschaften von (GaIn)(NAs)-Laserdioden

Das Themengebiet der Arbeit war die Herstellung und Untersuchung von Halbleiterheterostrukturen und Laserbauelementen auf der Basis des neuartigen Materialsystems (GaIn)(NAs). Die Proben wurden mittels Metallorganischer Gasphasenepitaxie (MOVPE) unter Verwendung der Quellen Tertiärbuthylarsin (TBAs)...

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Bibliographic Details
Main Author: Nau, Siegfried
Contributors: Stolz, Wolfgang (Dr. habil) (Thesis advisor)
Format: Doctoral Thesis
Published: Philipps-Universität Marburg 2004
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The subject of this thesis was the production and the investigation of semiconductor heterostructures and laser devices based on the novel material system (GaIn)(NAs). The samples were produced by means of metal organic vapour phase epitaxy (MOVPE) by using the alternative sources tertiary-butyl-arsine (TBAs), 1,1-dimethyl-hydrazine (UDMHy), three-methyl-Gallium (TEGa) and three-methyl-Indium (TMIn) with growth temperatures of 525°C and a reactor pressure of 50mbar. As substrate exactly orientated (100)-GaAs was used. (GaIn)(NAs) is a metastable material system, which shows complex correlations between its growth parameters. The samples were analysed with several experimental methods. Some of these methods have been new created within the scope of this thesis. The thesis focuses on two points: On the one hand the structure and the structure development of (GaIn)(NAs)-heterostructures have been investigated. The special area of interest was then the shape of interior in the crystal embedded hetero interfaces and their influence on the electronic sample properties. On the other hand laser devices based on (GaIn)(NAs), which emit nearby 1300nm, have been produced and analysed because of the technological relevance. For the structural investigation of interior semiconductor interfaces a novel method was developed. Because of the combination of extremely selective corrodents and following atomic force microscopy (AFM) the novel method enables the observation of dynamic structure building proceedings on interior interfaces with a time resolution of one second at subatomic height resolution and a lateral resolution of about 20nm. With that one receives three-dimensional images of real interior interfaces. The way of function and the function ability was demonstrated for the material systems AlAs/GaAs, AlAs/(GaIn)As, AlAs/Ga(NAs) and AlAs/(GaIn)(NAs) in detail. The material systems GaAs, (GaIn)As and Ga(NAs) show under optimized growth conditions two-dimensional van der Merwe-growth. During growth interruptions the growth surfaces smooth out and smooth terraces, a monolayer high, are built. For the temporally development of characteristic structure sizes, in this case of island diameters, a power rule was found in the form of d=C*t^g. It describes quantitatively the structural development over more than two orders of magnitude. By contrast (GaIn)(NAs)-quantum wells (x[In]=30%, y[N]<3%) show the formation of two-dimensional islands. During growth interruptions (solely under TBAs stabilization) (GaIn)(NAs) interfaces roughen and show a novel, non continuous structural development. After a critical interruption time the entire quantum well material is involved. These processes have nothing to do with phase separation (the cubic order of the crystal is maintained) and they are independent of the macroscopic strain of the epi-layer. Stabilization with TBAs and UDMHy during growth interruption slows down or even stops these processes. (GaIn)(NAs) does not only show an uncommon structural formation itself it also changes the growth characteristics of the other materials in the heterostructure. Embedding (GaIn)(NAs)-quantum-wells can lead to a substantial change of the growth characteristic of Ga(N)As-barriers. These phenomena have been attributed to a laterally inhomogeneous strain distribution in the active material. The structural properties affect the electronic sample properties and device performance. To correlate growth parameters of (GaIn)(NAs)-material with device performance, systematically (GaIn)(NAs)-laser-diodes in wide stripe geometry have been investigated. It has been found that it is important to discriminate the growth of the aluminum containing cladding layers and the nitrogen containing active material in two different growth machines. On the top of this a strong correlation of the carbon content in the active material (determined by means of SIMS) and the threshold current density of laser devices have been found. The connection is valid over more than two orders of magnitude. The manner and the physical loss mechanism of the carbon defect are subjects of the current research. The process technology for wide stripe laser diodes and the set up of a powerful pulsed LIV-measurement system are described in detail in the appendix of this thesis (100ns pulse width, up to 4A pulse height).