Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

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

DS 9.2: Vortrag

Montag, 25. Februar 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 700^∘C to 800^∘C in 10^∘C 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 750^∘C we found two fully strained InGaN layers. Below 750^∘C only the first InGaN layer was fully strained. At temperatures below 750^∘C 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 750^∘C an interplay of indium segregation and strain is the dominating process, resulting in the growth of fully strained InGaN layers with different indium content.