Abstract
Transmission electron microscopy (TEM), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy were used in order to study the microstructure and optical properties of GaN films grown by metal-organic chemical vapor deposition (MOCVD) on c-plane sapphire by lateral confined epitaxy (LCE). In this method, the substrate is etched prior to growth to form uniform mesas separated by trenches for laterally restricting growth area. As previously observed for LCE GaN on Si(111), the density of threading dislocations was significantly reduced in the areas close to the edge of mesas due to the lateral propagation of the dislocations. Hence, the overall material quality improves with decreasing mesa size, which is consistent with the observed increase in photoluminescence band edge peak intensity. Electron diffraction indicated ∼1° rotation about the [\(1\bar 100\)] axis between the mesa and trench material, which was also observed in the image contrast of these two regions with g=\(11\bar 20\). Additionally, LCE samples prepared in [\(1\bar 100\)] and [\(11\bar 20\)] cross sections were used for comparing the growth rates in these two perpendicular directions. As theoretically expected, growth in the [\(11\bar 20\)] direction appears to proceed considerably faster than that in the [% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9qqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaaig% daceaIYaGbaebacaaIWaaaaa!38D1!\[11\bar 20\]] direction.
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It is important to note that the MOCVD reactor geometry in this case was a vertical showerhead configuration, in which the substrate is mounted on a rotating stage and held normal to the gas flow. Therefore, no directional effect is expected due to the reactor geometry or gas flow direction.
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Wu, F., Zamir, S., Meyler, B. et al. Microstructure of GaN grown by lateral confined epitaxy 2. GaN on patterned sapphire. J. Electron. Mater. 32, 23–28 (2003). https://doi.org/10.1007/s11664-003-0248-2
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DOI: https://doi.org/10.1007/s11664-003-0248-2