Variable temperature-scanning Hall probe microscopy with GaN/AlGaN two-dimensional electron gas (2DEG) micro Hall sensors in 4.2-425 K range using novel quartz tuning fork AFM feedback
Date
2008Source Title
IEEE Transactions on Magnetics
Print ISSN
0018-9464
Publisher
IEEE
Volume
44
Issue
11
Pages
3255 - 3260
Language
English
Type
Conference PaperItem Usage Stats
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Abstract
In this paper, we present the fabrication and variable temperature (VT) operation of Hall sensors, based on GaN/AlGaN heterostructure with a two-dimensional electron gas (2DEG) as an active layer, integrated with quartz tuning fork (QTF) in atomic force-guided (AFM) scanning Hall probe microscopy (SHPM). Physical strength and a wide bandgap of GaN/AlGaN heterostructure makes it a better choice to be used for SHPM at elevated temperatures, compared to other compound semiconductors (AlGaAs/GaAs and InSb), which are unstable due to their narrower bandgap and physical degradation at high temperatures. GaN/AlGaN micro Hall probes were produced using optical lithography and reactive ion etching. The active area, Hall coefficient, carrier concentration, and series resistance of the Hall sensors were ∼1 × 1 μm, 10 mΩ/G at 4.2 K, 6.3 × 10 12 cm -2 and 12 kΩ at room temperature and 7 mΩ/G, 8.9 × 10 12 cm -2 and 24 kΩ at 400 K, respectively. A novel method of AFM feedback using QTF has been adopted. This method provides an advantage over scanning tunneling-guided feedback, which limits the operation of SHPM the conductive samples and failure of feedback due to high leakage currents at high temperatures. Simultaneous scans of magnetic and topographic data at various pressures (from atmospheric pressure to high vacuum) from 4. to 425K will be presented for different samples to illustrate the capability of GaN/AlGaN Hall sensors in VT-SHPM.
Keywords
Atomic force microscopy (AFM)GaN/AlGaN heterostructure
Hall probe
Quartz tuning fork (QTF)
Scanning Hall probe microscopy (SHPM)
Compound semiconductors
Elevated temperature
Leakage currents