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Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 9: Semiconductor Nanophotonics: Materials, Models, Devices - GaN based Photonics II

DS 9.2: Talk

Monday, February 25, 2008, 16:30–16:45, H 2032

Analysis of the growth mechanisms for InGaN alloys in MOVPE — •Martin Leyer, J. Stellmach, M. Pristovsek, and M. Kneissl — Technische Universität Berlin, Institut für Festkörperphysik, Sekr. EW 6-1, Hardenbergstr. 36, 10623 Berlin

The realisation of light emitting devices and lasers in the green spectral range requires high quality InGaN layers with an Indium content of 20% or more. However, the growth of such is very challanging due to layers shows phenomena like binodal decomposition and strain, resulting in a significant reduction of the efficiency in these devices. To understand the mechanism of InGaN growth, thick (∼200 nm) layers were grown on GaN/sapphire templates. The growth temperature was systematically changed from 700C to 800C in 10C steps. In-situ spectroscopic ellipsometry allowed to determine growth rate and surface roughness. XRD ω−2Θ measurements yield two main peaks up to growth temperatures of 790 C. The indium incorporation varies between 0.19%/C for the first and 0.39%/C for the second InGaN layer. Reciprocal space mapping around the (1 0 . 5) reflex revealed two growth regimes, indicating two different growth mechanisms. For temperatures above 750C we found two fully strained InGaN layers. Below 750C only the first InGaN layer was fully strained. At temperatures below 750C first a fully strained layer grows up to a critical layer thickness. Exceeding this critical thickness the growth mode changes from 2D to 3D. Above 750C an interplay of indium segregation and strain is the dominating process, resulting in the growth of fully strained InGaN layers with different indium content.

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