Characteristics of Gated GaAs/Al0.3Ga0.7As Heterostructures

Abstract

Two devices of different gate areas are fabricated on the shallow GaAs/Al0.3Ga0.7As heterostructures and their conductance and capacitance characteristics are studied and compared. Longitudinal magnetoresistance is affected significantly by the gate area while no change has been observed for Hall magnetoresistance. A carrier concentration of 6 × 1015 m–2 and 2 × 1015 m–2 at zero gate bias and a mobility of 23.2 m2 V–1 s–1 and 5.3 m2 V–1 s–1 for big and small gate devices, respectively, are obtained. A strong shift in the capacitance behavior is observed between 180 and 120 K, which confirms the effect of DX centers. Under bias cooling, the 2DEG channel is depleted at more negative voltages which demonstrates the suppression of the DX center effect. Magnetoresistance and magnetocapacitance measurements showed that the carrier density depends linearly on the gate voltage in the negative bias, whereas no change has been observed with positive bias.