Scanning Hall Probe Microscopy has become a widely used method for magnetic field measurements in the last decade. For Scanning Hall Probe Microscopy, low noise Hall sensors are fabricated from GaAs and InAs structures using optical lithography techniques. Noise analysis of both types of sensors are done at 77 K and 300 K for various Hall currents. Minimum detectable magnetic fields are calculated from these noise measurements. The range of the Hall currents that makes the sensors work most efficiently are also calculated.