2-DIMENSIONAL ELECTRON-GAS FORMED IN A BACK-GATED UNDOPED HETEROSTRUCTURE

By using a back-gate operation, a high-quality two-dimensional electro n gas (2DEG) is formed in an undoped GaAs/AlGaAs inverted heterostruct ure. A high mobility of around 3 x 10(6) cm(2)/V s at 1.6 K is obtaine d for the structure without any compensating surface doping. The elect ron density is controllable down to 7 x 10(9) cm(-2). The relation bet ween electron density and mobility is studied for samples both with an d without a surface gate. The obtained results indicate that backgroun d impurities and an inhomogeneity of the electric field coming from th e surface govern the mobility in a low-electron-density region and tha t the interface inhomogeneity becomes important at a high electron den sity. (C) 1998 American Institute of Physics. [S0003-6951(98)02214-1].