We have investigated the electrical and thermoelectrical properties of 30-nm-thick InAs nanowires in a temperature range between T = 200 K and T = 350 K. Devices were fabricated that allow the measurement of the conductivity and Seebeck coefficient upon the application of a gate voltage. The carrier concentration in the NWs could be varied by two orders of magnitude. The dependence of the Seebeck coefficients measured on the carrier concentration is similar to bulk InAs. A temperature-dependent mobility of IL = 1200-1400 cm ²/Vs of these unpassivated NWs could be determined from both the transistor characteristics and Seebeck coefficient measurements.