ANALYTICAL NOISE MODEL WITH THE INFLUENCE OF SHOT-NOISE INDUCED BY THE GATE LEAKAGE CURRENT FOR SUBMICROMETER GATE-LENGTH HIGH-ELECTRON-MOBILITY TRANSISTORS

A new high-frequency noise model which takes into account the influenc e of shot noise induced by the gate leakage current is introduced; the model accurately explains the observed minimum noise figure of submic rometer gate-length HEMT's as a function of frequency. Based on the st eady-state Nyquist theorem for multiterminal devices recently reported [1], the minimum noise figure and the corresponding optimum source im pedance of the microwave field effect transistors are expressed as fun ctions of the measurable device parameters including noise spectral in tensities and small-signal circuit parameters. The derived minimum noi se figure can be shown to reduce to a simple form, i.e., an empirical relation with two fitting constant. The simple form and the derived fo rmulas for the optimum source impedance can explain very well the expe rimental findings of the submicrometer gate-length high electron mobil ity transistors over the extended microwave frequency range and also p rovide the informations needed for the design of microwave low noise a mplifiers.