Abstract: A semiconductor light emitting device includes a Group-III nitride semiconductor layer on a buffer layer. The buffer layer includes a first layer, a second layer, and a third layer in that order. Each of the first layer, the second layer, and the third layer includes a composition which includes aluminum (Al), nitrogen (N), and oxygen (O). A minimum or average value of an oxygen concentration (atoms/cm3) of each of the first layer and the third layer is greater than an oxygen concentration (atoms/cm3) of the second layer.

Abstract: A thin film deposition apparatus includes a reaction chamber, a main disk installed in the reaction chamber, and a gas discharging unit disposed outside the main disk. The gas discharging unit recollects a gas in the reaction chamber, and includes: a base member that includes an outer sidewall, an inner sidewall, and a lower wall that connects the outer and inner sidewalls, and is ring-shaped with an open upper portion. At least one through hole is formed in the lower wall. A discharge sleeve is configured to be inserted into the through hole, wherein a gas outlet is formed in the discharge sleeve. An upper cover that is ring-shaped covers the open upper portion of the base member. A plurality of gas inlets are formed in the upper cover.