A method of reducing the density of threading dislocations in light emitting devices, by the selective creation of cavities

摘要

A semiconductor light-emitting device comprises a substrate 101 and a semiconductor layer structure disposed over the substrate. The device particularly relates to Nitride based LEDâ s or lasers, in particular (Al,In,Ga)N deposited on sapphire, silicon, silicon carbide or GaN substrates. The layer structure includes a first layer 102 disposed over the substrate, a second layer 105, and an active region 104 for light emission disposed between the first layer 102 and the second layer 105. One or more cavities 108 are present in the layer structure, each cavity coincident with a respective threading dislocation 103 of at least a first type that extends generally through the layer structure, and a cavity extending from an upper surface of the layer structure through at least the second layer 105 and the active region 104. By removing material at the location of a dislocation, the invention provides effective suppression of the tendency of the threading dislocations to act as non-radiative centers, which improves the light output efficiency. The device may be manufactured by a two-stage method that has a first etching step of selectively etching the layer structure at one or more locations at which a respective threading dislocation is present thereby to form a pilot cavity at the or each location. A second etching step is applied to increase the depth of the or each pilot cavity to produce a respective cavity 108 that extends at least through the second layer 105 and the active region 104.