LOW-TEMPERATURE SUBBAND 2D ELECTRON MOBILITIES IN HEAVY DELTA-DOPED AND MODULATION-DOPED GAAS GAALAS HETEROSTRUCTURES/

We synthesised high-2D electron-density GaAs/GaAlAs heterostructures w ith different distance L(delta) of Si delta-layer in GaAs from the het erojunction and uniform doped GaAlAs. The quantum Hall effect and Shub nikov-de Haas effect were measured for temperatures down to 0.4 K in m agnetic fields up to 40 T. The enhanced 2D electron concentration achi eved was 1.110(13) cm(-2) in six filled subbands. The Hall mobility d epends on L(delta) and has maximum for L(delta) = -600 + 750 Angstrom. From the amplitudes of the SdH oscillations and Fourier transforms th e subband mobilities and electron concentration in each subband have b een extracted. According to calculations intersubband electron scatter ing appears to be important and reduces mobilities in subbands.