A phosphor and a method of deposition. The phosphor comprises a composition of
the formula MaBa1-aM";2M";4;
RE, where
M is at least one element selected from magnesium and calcium,
M"; is at least one element selected from aluminum, gallium and indium, M";
is at least one element selected from sulphur, selenium and tellurium, RE is at
least one rare earth element, especially europium or cerium, and 0
