| As a new type of solid state light source, GaN-based LEDs(light-emitting diodes)have has the advantages of low-power, long-life and high-luminescence efficiency. It will play an increasingly important role in display, light and instructions. GaN and its associated ternary or quaternary compounds are highly welcomed by the market due to the realization of the whole visible spectrum coverage after combination in recent years. At present, the MOCVD(Metalorganic Chemical Vapor Deposition) equipment is still the mainstream way to grow GaN material. However, this method will inevitably lead to the foreign impurities adsorption such as C and O, which would have a great effect on the performance of devices. In addition, as recently reported, the impurities shown different characters in different polarity films and even have an influence on the adsorption of other important elements(such as In).Based on this background, we applied normal and practical sapphire substrates to obtain a series of different planes of GaN films. We also compare impurities absorption of C and O in different polarity films and obtain some conclusions. Also, research hotspot on the combination efficiency of Indium in semi-polar plane is preliminary studied, the main research work is as follows:We compare the absorption of C and other impurities in different polarity GaN films and conduct the quantitative analysis through SIMS(Secondary Ion Mass Spectroscopy). A higher C concentration is found in Ga-plane than N-plane, shown that the polarity actually affect the C absorption. According to the comparison of the yellow-band of PL spectrum,we observe that the non-polar a-plane contains higher C than the c-plane. The relevant explanation is also given. In addition, the C concentration change in a-plane and c-plane GaN appear an opposite trends(increasing with temperature in a-plane and decreasing in c-plane). All the results show that C absorption is sensitive to the environments and extremely complicated, polarity or temperature may become the dominant factor.We observe the change trend of O and find that the N-plane owns nearly two orders of magnitude of O concentration than Ga-plane. And the a-plane GaN also owns higher O concentration than the c-plane GaN, which above show that N- and non-polar plane have a strong ability of O adsorption. Meanwhile, the change of temperature strongly effect the morphology and the crystal quality, also the O adsorption. The O concentration is decreasing with the temperature increase, which is different from previous results have been reported. It is proved by related experiments that the morphology evolution caused by temperature effect the finally O absorption, indicating that morphology also affect the O absorption.The H absorption is not influenced by the temperature. However, an obvious H concentration change between semi-polar and polar plane show polarity affect the H absorption. We also find Si absorption is only influenced by the temperature, and the Si concentration increases with a rise of temperature. In addition, the change of H has an closely link with In when the compound contains In. Furthermore, we also conclude experimentally and theoretically In absorption in semi-polar plane is slightly higher than that in the polar plane. |
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