HIGHLY SENSITIVE AL0.25GA0.75AS IN0.25GA0.75AS/GAAS QUANTUM-WELL HALLDEVICES WITH SI-DELTA-DOPED GAAS LAYER GROWN BY LP-MOCVD/

Quantum-well Hall devices based on Si-delta-doped Al0.25Ga0.2As/In0.25 Ga0.75As/GaAs pseudomorphic heterostructure materials grown by the low -pressure metal organic chemical vapour deposition (LP-MOCVD) method h ave been successfully fabricated. A Si-delta-doped GaAs layer is intro duced for the first time in the Hall device to reduce the thermal vari ation of electron concentrations and to improve its temperature charac teristics. A high electron mobility of 8100 cm(2) V-1 s(-1) with a she et carrier density of 1.5 X 10(12) cm(-2) has been achieved at room te mperature. A temperature coefficient of - 0.015% K-1 with a product se nsitivity of 420 V A(-1) T-1 has been obtained. High signal-to-noise ( S/N) ratios corresponding to minimum detectable magnetic fields (B-min ) of 60 nT at 1 kHz and 110 nT at 100 Hz have been attained due to the reduced low-frequency noise from DX centres and the high mobility, Th ese data belong to one of the best reported results.