Low-frequency noise and mobility fluctuations in AlGaN/GaN heterostructurefield-effect transistors

The l/f low-frequency noise characteristics of AlGaN/GaN heterostructure he ld-effect transistors, grown on sapphire: and SiC substrates by molecular b eam epitaxy and organometallic vapor phase epitaxy, are reported. The Hooge parameter is deduced taking into account the effect of the contact noise a nd the noise originating in the ungated regions. A strong dependence betwee n the Hooge parameter and the sheet carrier density is obtained, and it is explained using a model in which mobility fluctuations are produced by disl ocations. A Hooge parameter as low as alpha(CH)approximate to 8 x 10(-5) is determined for devices grown on SiC substrates. (C) 2000 American Institut e of Physics. [S0003-6951(00)02623-1].