Electroluminescence from GaInN Quantum Wells Grown on Non-(0001) Facets of Selectively Grown GaN Stripes
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Electroluminescence from GaInN Quantum Wells Grown on Non-(0001) Facets of Selectively Grown GaN Stripes
Barbara Neubert1 , Frank Habel1 , Peter Bruckner1 , Ferdinand Scholz1 , Till Riemann2, Jurgen Christen2 1 Optoelectronics Department, University of Ulm 89069 Ulm, Germany 2 Institute for Experimental Physics, Otto-von-Guericke Univ. Magdeburg 39106 Magdeburg, Germany ABSTRACT
Non (0001) GaInN QWs have been grown by low pressure MOVPE on side facets of triangular shaped selectively grown GaN stripes. By analysing low temperature photo- and cathodoluminescence and room temperature electroluminescence, we found strong indications, that both, In and Mg are less eÆciently incorporated on these side facets compared to the common (0001) plane with even lower eÆciency for stripes running along (1-100) compared to (11-20). Nevertheless, we observed strong light emission from these quantum wells, supposed to be at least partly caused by the reduced piezo-electric eld. INTRODUCTION
The Group III nitrides play an important role for light emitting devices, because their spectra reach from UV to visible wavelengths. High brightness LEDs and laser diodes have been fabricated. Due to their strong polarity, group III nitrides show large piezoelectric constants along the axis. Therefore strong piezoelectric elds (PFs) are induced in biaxially strained GaInN quantum wells (QWs) grown on such (0001)-oriented GaN. This gives rise to a spatial separation of the electron and hole wave functions what hampers their radiative recombination. A higher probability for radiative recombination can be expected for QWs grown along directions other than the most commonly used [1,2], thus potentially leading to improved optical characteristics for light emitting devices. To this end, some groups have investigated the growth of a-plane structures on r-plane sapphire. However, up to now only lower quality layers with a large dislocation density could be grown [3]. Therefore, we have grown GaInN QWs on non-(0001) facets of selectively deposited GaN stripes with triangular cross-section, where we expect reduced PFs with still low defect densities. In order to evaluate their geometry and facet dependent optoelectronic properties, they have been investigated by photo-, cathodo- and electroluminescence. EXPERIMENT
The samples under study have been grown by low pressure metal organic vapor phase epitaxy (MOVPE) in a conventional horizontal reactor. A 1.5 m thick GaN template was grown rst on c-plane sapphire, then was covered with a 200 nm SiO2 mask by plasma enhanced chemical vapor deposition (PECVD) and structured by conventional optical lithography and reactive ion etching (RIE) to serve as regrowth mask. We patterned the
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SiO2 with two stripe directions perpendicular to each other to get stripes along < 1100 > and < 1120 > orientation. The dimensions of the mask openings and mask periods ranged from 4 to 8 m and from 6 to 300 m, respectively. We generated silicon doped GaN stripes with triangular shape having (1122)-facet
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