A method of making a channel substrate buried heterostructure InP/(In,Ga)(As,P) laser avoids the need to use two separate stages of epitaxial growth by using a channel in a (100) surface substrate 1 extending in the [011] direction with {111}B sides. This allows the channel to be made before the growth of an (In,Ga)(As,P) blocking layer 3 which can be grown under conditions which do not require the use of a mask to prevent nucleation on the channel sides. The same technique is also applicable to the manufacture of a terraced substrate laser incorporating a blocking layer.