Abstract
We study room-temperature performance of micro-Hall magnetic sensors based on pseudomorphic GaAlAs/GaInAs heterostructures. Active areas of our sensors range from 1 to 80 microns. We focus on the smallest detectable magnetic fields in small sensors and perform a systematic study of noise at room temperature in the frequency range between 1 Hz and 100 kHz. Our data are interpreted by the mobility fluctuation model. The Hooge parameter is determined for the applied technology. We show that, independently of the experimental frequency, the ratio of sensitivity to noise is proportional to characteristic length of the sensor. The resolution of $1\, miliGauss/ \sqrt{Hertz}$ is achievable in a $3 \mu$m sensor at room temperature .