The sub-micrometer thickness n-InSb/i-GaAs epilayers for magnetoresistor applications at room temperatures of operation

Abstract

Magnetotransport at fields up to 500 mT and LF-noise characteristics are reported for miniature magnetoresistors with ferrite concentrators based on Sn-doped n-InSb/i-GaAs heterostructures grown by MBE. The thickness of the InSb epilayers lie in the range 0.55– 1.5 μm giving room temperature mobilities of 2.5– 5.5 m 2 V −1 s −1 with carrier densities of (0.5– 1.5)×10 17 cm −3 . The room temperature magnetoresistance (MR) for our two terminal devices could be as high as 115% at 50 mT which is comparable to the extraordinary MR (ExMR) recently reported in microscopic composite van der Pauw disks four terminal devices [Science 289 (2000) 1530]. In addition, a high signal-to-noise ratio and a good temperature stability of R( B)/ R 0=0.5– 0.83% K −1 was observed for B<60 mT (below the saturation field B sat for ferrite). Device resistance stability R 0( T) was equal to 0.27– 0.66% K −1 in zero field with a nominal device resistance R 0=197– 224 Ω for DC currents in the range I=0.01– 1.0 mA . The minimum detectable magnetic field is estimated from the reduced differential MR ( ∂R/∂B)/R=2000% T −1 at B=31 mT and normalised 1/ f current noise power spectral density measured at the same field. The resolution limit B min =2.6 nT at 10 2 Hz and B min =0.82 nT at 10 3 Hz . These resolution limits are seven times better than those recently reported for the same material n-InSb/i-GaAs and ferrite fabricated Hall sensors [Magnetotransport and Raman characterization of n-InSb/i-GaAs epilayers, for Hall sensors applications over extremely wide ranges of temperature and magnetic field, Proceedings NGS 10, IPAP Conference Series 2, IPAP, Tokyo, 2001, pp. 151–154].