In the early 1960s, Alferov organized an effort at Ioffe Institute to develop semiconductor heterostructures. Semiconductor heterojunctions transistors enabled higher frequency use than their homojunction predecessors, and this capability plays a key role in modern mobile phone and satellite communications. Alferov and colleagues worked on GaAs and AlAs III-V heterojunctions. A particular focus was the use of heterojunctions to create semiconductor lasers capable of lasing at room temperature. In 1963, Alferov filed a patent application proposing double-heterostructure lasers; Herbert Kroemer independently filed a US patent several months later. In 1966, Alferov's lab created the first lasers based on heterostructures, although they did not lase continuously. Then in 1968, Alferov and coworkers produced the first continuous-wave semiconductor heterojunction laser operating at room temperature. This achievement came a month ahead of Izuo Hayashi and Morton Panish of Bell Labs also producing a continuous-wave room-temperature heterojunction laser.