2 September 2005 ZnO semiconductors for lighting
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Intentionally doped n-type bulk ZnO has been grown by patented melt technique at Cermet and was used as a substrate for homo-epitaxial growth of p-type ZnO films. The n-type ZnO has a carrier concentration on the order of 1018cm-3 with a mobility of 113cm2/Vs, which is good for optical devices. Secondary ion mass spectroscopy (SIMS) profile shows a very uniform distribution of n-type dopant in the ZnO. Excellent transmission from the sharp absorption edge through the visible portion of the spectrum indicates that as grown n-type ZnO is perfect for any optical device applications. P-type ZnO thin films were successfully grown by MOCVD technique on n-type ZnO substrate to form ZnO based p-n junction structure. Cadmium and magnesium doped ZnO films were also grown by MOCVD and resulted in tunable bad gap energy of ZnO based alloy. Ohmic contact layer on n-type ZnO was formed by using Ti/Au and on p-type ZnO was formed by using Ni/Au. The current-voltage (I-V) characteristics of the ZnO based p-n junction exhibited rectification when reverse biased with a breakdown voltage of 10 V and turn-on voltage of 3.3 V. Post anneal of p-type ZnO films showed big improvement on the I-V characteristics. Electroluminescence (EL) spectra obtained from devices driven to 40mA are dominated by a peak at 384nm.
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Jeff Nause, Ming Pan, Varatharajan Rengarajan, William Nemeth, Shanthi Ganesan, Adam Payne, Nola Li, Ian Ferguson, "ZnO semiconductors for lighting", Proc. SPIE 5941, Fifth International Conference on Solid State Lighting, 59410D (2 September 2005); doi: 10.1117/12.624534; https://doi.org/10.1117/12.624534

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