A semiconductor light-emitting device and a method of manufacture thereof A method of manufacturing a semiconductor light-emitting device comprises selectively etching a semiconductor layer structure (16) fabricated in a nitride materials system and including an aluminium-containing cladding region or an aluminium-containing optical guiding region (5). The etching step forms a mesa (17), and also exposes one or more portions of the aluminium-containing cladding region or the aluminium-containing optical guiding region (5). The or each exposed portion of the aluminium-containing cladding region or the aluminium-containing optical guiding region (5) Is then oxidised to form a current blocking layer (18) laterally adjacent to and extending laterally from the mesa. When an electrically conductive contact layer (11) is deposited, the current blocking layer (18) will prevent the contact layer (11) from making direct contact with the buffer layer (3).