Imaging capability of pseudomorphic high electron mobility transistors, AlGaN/GaN, and Si micro-Hall probes for scanning Hall probe

The authors present a comparative study on imaging capabilities of three different micro-Hall probe sensors fabricated from narrow and wide band gap semiconductors for scanning hall probe microscopy at variable temperatures. A novel method of quartz tuning fork atomic force microscopy feedback has been used which provides extremely simple operation in atmospheric pressures, high-vacuum, and variable-temperature environments and enables very high magnetic and reasonable topographic resolution to be achieved simultaneously. Micro-Hall probes were produced using optical lithography and reactive ion etching process. The active area of all different types of Hall probes were 1 1 m2. Electrical and magnetic characteristics show Hall coefficient, carrier concentration, and series resistance of the hall sensors to be 10 m /G, 6.3 1012 cm−2, and 12 k at 25 °C and 7 m /G, 8.9 1012 cm−2 and 24 k at 125 °C for AlGaN /GaN two-dimensional electron gas 2DEG , 0.281 m /G, 2.2 1014 cm−2, and 139 k at 25 °C and 0.418 m /G, 1.5 1014 cm−2 and 155 k at 100 °C for Si and 5–10 m /G, 6.25 1012 cm−2, and 12 k at 25 °C for pseudomorphic high electron mobility transistors PHEMT 2DEG Hall probe. Scan of magnetic field and topography of hard disc sample at variable temperatures using all three kinds of probes are presented. The best low noise image was achieved at temperatures of 25, 100, and 125 °C for PHEMT, Si, and AlGaN /GaN Hall probes, respectively. This upper limit on the working temperature can be associated with their band gaps and noise associated with thermal activation of carriers at high temperatures.