The magneto-transport of a GaAs FET having a Si atomic layer doped lay
er as the conducting channel was studied as a function of the carrier
density in the channel. The negative magneto-resistance (NMR) was obse
rved at cryogenic temperatures (4.2-40 K), which was enhanced by incre
asing the gate voltage, i.e., by decreasing the carrier density. By in
creasing the magnetic-field, however, the NMR reaches a saturated cons
tant, of which magnitude was increased by increasing the gate voltage.
By normalizing the magnetic field and the magnitude of the NMR by a c
onstant, we found that the behavior of the initial increase followed b
y the saturation is expressed by a unified function irrespective to th
e gate voltage. The unified function was determined by the Concentrati
on of Si atoms. (C) 1998 Elsevier Science Ltd. All rights reserved.