Observation of Hot-Electron Shot Noise in a Metallic Resistor

We have measured the current noise of silver thin-film resistors as a function of current and temperature and for resistor lengths of $7000$, $100$, $30$, and $1\mu \mathrm{m}$. As the resistor becomes shorter than the electron-phonon interaction length, the current noise for large current increases from a nearly current independent value to the interacting hot-electron value $(\sqrt{3}/4\mathrm{})2eI$. However, further reduction in length below the electron-electron interaction length decreases the noise to a value approaching the independent hot-electron value $\left(1/3\right)2eI$ first predicted for mesoscopic resistors.