Magneto-transport studies in AlGaN/GaN MODFETs

In order to characterise the transport properties of the 2DEG in AlGaN/GaN modulation doped field effect transistors, channel magnetoresistance has been measured in the magnetic field range 0-12 T, the temperature range 25-300 K and gate bias range +0.5 V to -2.0 V. Assuming that the 2DEG provides the dominant contribution to the total conductivity, a one carrier fitting procedure has been applied to extract electron mobility and carrier density at each particular value of temperature and gate bias. Consequently, the mobility versus 2DEG density has been obtained for each different temperature. The qualitative analysis of these profiles and comparison with theoretical predictions published by others suggests that for 2DEG densities below 7/spl times/10/sup 12/ cm/sup -2/ the electron mobility is limited by impurity scattering, whereas for densities above this level and up to 1/spl times/10/sup 13/ cm/sup -2/ the electron mobility is controlled by AlGaN/GaN interface roughness.