The book presents a generalization of the accumulated experience in creating transistors based on wide-band materials, in particular, transistors on heterostructures of the Al. type. GaN/GaN and microwave devices based on them. The properties of wide-band semiconductors, methods of their production and research, as well as methods for creating heterostructures on various substrates are described in detail. The physics of heterojunctions and two-dimensional gas carriers . The technology of production of transistors is analyzed in detail taking into account the existing experience of their real manufacture. The parameters of transistors are given and the characteristics of promising directions in the field of their use are provided. Various systems on the crystal and in the body, created on the basis of heterotransistors of the Al. type, are considered. GaN/GaN/Al2. O3 and Al. GaN/GaN/SiC. The book will be useful to specialists in the field of electronics, researchers, practicing engineers and developers of electronic equipment. Formation of microwave signals in modern solid-state radio-electronic radio systems . Providing high-quality signals using microwave devices on new semiconductor materials. Microwave transistor designs on wide-band materials and heterostructures. Technological processes of creating GaN microwave transistors and integrated circuits . Control of heterostructure parameters in the process of development and production . Control of technology, parameters and reliability of GaN-transistors .