Method of growing a semiconductor multi-layer structure

A method of growing an (In,Ga)N layer structure by molecular beam epitaxy comprising the steps of:

• a) disposing a substrate in a growth chamber;
• b) growing a first (In,Ga)N layer having a first indium mole fraction over the substrate at a substrate temperature of at least 650° C.;
• and
• c) varying the rate of supply of indium to the growth chamber thereby to grow a second (In,Ga)N layer having a second indium mole fraction different from the first indium mole fraction over the first (In,Ga)N layer at a substrate temperature of at least 650° C.;
• wherein the rates of supply of ammonia and gallium to the growth chamber are kept substantially constant during the growth of the first and second layers, and
• wherein at least one of the first (In,Ga)N layer and the second (In,Ga)N layer is an InGaN layer, and the substrate temperature during the growth of the at least one InGaN layer is in the range 650° to 800° C.