Integrated circuits - The case for gallium arsenide

Various GaAs semiconductor devices, their performances, and manufacturing techniques for electronic devices and circuits are described. Consideration is given to depletion MESFETs (D-MESFETs), enhancement mode MESFETs (E-MESFETs) and the high electron mobility transistor (HEMT). GaAs is favored over Si ICs due to the higher electron mobility in the GaAs medium, as well as a large functioning range, -200 to 200 C temperature. The HEMT feature a fast turn-on, which is an advantage at lower temperatures, where the other MESFETs are hindered in performance. Manufacturing of the D-MESFETs is facilitated by channel resistance characteristics, although power dissipation features commend the implementation of E-MESFETs for VLSI applications. Molecular beam epitaxy is used to fabricate heterojunction GaAs devices, and bipolar transistors produced by MBE show a potential for switching delays lower than 10 picosec. Raw materials technologies are presently yielding GaAs ingots up to 3 in. in diam.