With this work we demonstrate a simple procedure to increase the extraction efficiency (ηextr) of GaN LEDs grown on sapphire substrate by using a thin ZnO layer to be used as p-type transparent conductive oxide. Roughening of the ZnO contact itself is engineered during the deposition of the ZnO by Low pressure Chemical Vapour Deposition technique (LP-CVD). To better study the contact properties 3 different layer thicknesses have been deposited: 100 nm, 1 μm and 2 μm. A reference sample has also been processed for comparison with standard Ni/Au semitransparent contact. The surface roughness measured by AFM indicates that the rms roughness (2x2μm2) increases from 12nm to 87nm for 100nm and 2μm of ZnO, respectively. This is explained by the separation of ZnO crystals which starts to appear for higher thicknesses, thus increasing the surface roughness.
Improved InGaN LED extraction efficiency by means of rough ZnO transparent contacts
TRIVELLIN, NICOLA;MENEGHESSO, GAUDENZIO;ZANONI, ENRICO;
2011
Abstract
With this work we demonstrate a simple procedure to increase the extraction efficiency (ηextr) of GaN LEDs grown on sapphire substrate by using a thin ZnO layer to be used as p-type transparent conductive oxide. Roughening of the ZnO contact itself is engineered during the deposition of the ZnO by Low pressure Chemical Vapour Deposition technique (LP-CVD). To better study the contact properties 3 different layer thicknesses have been deposited: 100 nm, 1 μm and 2 μm. A reference sample has also been processed for comparison with standard Ni/Au semitransparent contact. The surface roughness measured by AFM indicates that the rms roughness (2x2μm2) increases from 12nm to 87nm for 100nm and 2μm of ZnO, respectively. This is explained by the separation of ZnO crystals which starts to appear for higher thicknesses, thus increasing the surface roughness.Pubblicazioni consigliate
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