The physics behind the one-dimensional electron-gas system (1D EG) is becoming very important for the design and characterization of ultrafast, semiconducting devices based on the high mobility of the 1D EG. In this work, we present the thermoelectric power of a quasi-one-dimensional electron-gas system formed in a narrow-channel high-electron-mobility transistor as a function of temperature, for different values of the one-dimensional electron density. © 1988 The American Physical Society.