  A simple hot electron thermocouple is realized in a two-dimensional electron
system (2DES) and used to measure the diffusion thermopower of the 2DES at zero
magnetic field. This hot electron technique, which requires no micron-scale
patterning of the 2DES, is much less sensitive than conventional methods to
phonon-drag effects. Our thermopower results are in good agreement with the
Mott formula for diffusion thermopower for temperatures up to T ~ 2 K.
