Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: III-V Semiconductors I (mainly Nitrides)

HL 29.10: Vortrag

Dienstag, 27. März 2012, 12:00–12:15, EW 201

Active region design and MOVPE growth of UV–B light emitting diodes — •F. Mehnke, J. Stellmach, T. Kolbe, M.-A. Rothe, C. Reich, T. Wernicke, M. Pristovsek, and M. Kneissl — Institute of Solid State Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

The external quantum efficiency of AlGaN–based ultraviolet (UV) light emitting diodes (LED) decreases with shorter emission wavelength. This is attributed to a higher defect density, carrier localization, increased magnesium acceptor ionization energy and an enhanced incorporation of impurities.

We studied the influence of active region and electron blocking layer (EBL) design on the injection efficiency. UV LEDs were grown by metalorganic vapour phase epitaxy (MOVPE) in a spectral range between 320 nm and 290 nm. The devices were characterized by electro– and photoluminescence spectroscopy and XRD. With increasing aluminium content in the active region i.e. decreasing emission wavelength we observe for an Al_0.6Ga_0.4N EBL a decrease of output power and increase of p–side luminescence. This indicates decreasing injection–efficiency due to a lower effective barrier height of the EBL. We will discuss the effect of the barrier height and magnesium doping on the injection efficiency and compare the results with 1D–drift–diffusion simulation.