MICROWAVE NOISE MEASUREMENTS ON AL0.3GA0.7AS GAAS CHANNELS GROWN BY MOLECULAR-BEAM EPITAXY USING AS-2 AND AS-4/

We present microwave noise measurements performed on different high el ectron mobility transistor channels under both darkness and illuminati on. Two structures of Alo(0.3)Gao(0.7)As/GaAs layers have been grown w ith beams of Asp and As-4 using molecular beam epitaxy. The measured r oom temperature, Hall mobilities and sheet carrier densities have demo nstrated in both cases a good de performance of the channels. However, the measurement of the noise temperature at 1.5 GHz has shown the sam ple grown with As-4 to be considerably noisier than the one grown with AS(4).