Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 52: Heterostructures
HL 52.6: Vortrag
Donnerstag, 25. März 2010, 11:30–11:45, H17
Theory of reduced built-in polarization in nitride-based [0001] quantum dots — •Stefan Schulz1 and Eoin P. O’Reilly1,2 — 1Tyndall National Institute, Lee Maltings, Cork, Ireland — 2University College Cork, Physics Department, Cork,Ireland
For energy-efficient solid state lighting, InGaN systems are promising candidates since the assistance of phosphor is not required for a white light source [1]. However, the emission efficiency of c-plane InGaN quantum wells (QWs) drops significantly when going to thicker QWs and/or higher indium content and therefore to longer wave length. This behavior is attributed to the strong electrostatic built-in field in nitride-based heterostructures grown along the c-direction.
Here, we use a surface integral method [2] to determine the polarization potential in QDs and QWs grown along the c-direction. We focus our attention in particular on InGaN nanostructures. Our analysis of the behavior of the electrostatic potential in these systems reveals that the field in QDs is strongly reduced compared to a QW of the same height. This reduction of the built-in field originates from two effects (i) a reduction of the [0001] surface area and (ii) strain redistributions in the QD system. The analysis is carried out for different QD geometries. Furthermore, because of the reduction of the built-in field in a QD compared to a QW of the same composition and height the indium content in the dot can be increased considerably for a fixed field value.
[1] C. J. Humphreys, MRS Bulletin 33, 459 (2008)
[2] D. P. Williams et al., Phys. Rev. B 72, 235318 (2005)