Transport in a gated Al0.18Ga0.82N/GaN electron system
Journal
Journal of Applied Physics
Journal Volume
94
Journal Issue
5
Pages
3181-3184
Date Issued
2003
Author(s)
Juang, J.R.
Huang, T.-Y.
Chen, T.-M.
Lin, M.-G.
Kim, G.-H.
Lee, Y.
Hang, D.R.
Chyi, J.-I.
Abstract
We have investigated the low-temperature transport properties of front-gated Al0.18Ga0.82N/GaN heterostructures. At zero gate voltage, the Hall mobility increases with decreasing temperature (20 K⩽T⩽190 K) due to a reduction in phonon scattering. For T⩽20 K, the mobility decreases with decreasing temperature. This is due to weak localization in a weakly disordered two-dimensional system. By changing the applied gate voltage, we can vary the carrier density n from 3.11×1012 to 6.95×1012 cm−2 in our system. The carrier density shows a linear dependence on the applied gate voltage, consistent with a simple parallel-plate capacitor model. The average distance between the GaN electron system and the AlGaN/GaN interface is estimated to be 240 Å. At high carrier densities (n>4.65×1012 cm−2), the measured mobility (μ) is found to be a decreasing function of carrier density as μ∼n−0.31. Loss of mobility with increasing carrier density is dominated by interface roughness scattering. At low carrier densities (n<4.24×1012 cm−2), the measured mobility is found to be an increasing function of carrier density as μ∼n0.34. This is consistent with remote ionized impurity scattering, although the measured exponent 0.34 is smaller than the typical value (0.7–1.5) observed in an AlGaN/GaN electron system. A possible reason is that our sample mobility is approximately five times lower than those in other devices for a similar electron density.
SDGs
Type
journal article