A low-noise InSb thin film hall element: Fabrication, device modeling, and audio application

Low-noise InSb thin film Hall elements have been developed as magnetic sensors for audio tape playback. Approximately 1.4-μm thick Hall elements are fabricated by vacuum deposition followed by microzone melting, film thinning, and subsequent heat treatment. After film thinning, electron mobility at room temperature is 6 m²/V . s showing the 1-ppm level impurity concentration. After heat treatment, noise is at the 0.5-μV level for frequencies in the 10²-10⁴Hz range and signal-to-noise ratio of the Hall elements is 82 dB in a 1-mT (10-G) magnetic flux density. The device characteristics as functions of dc bias current is successfully computer-simulated, where element Joule heating is taken into account. The calculated results agree quantitatively with the experimental results. For this device modeling, electrical transport properties in InSb crystals are calculated and related to element temperature and ionized-impurity concentrations. In order to apply the Hall elements to audio magnetic heads for cassette tape playing, the head design principle and the head signal-to-noise ratio are clarified for the first time. The advantages of the Hall effect magnetic heads are also discussed.