Based on investigating the effects of isoelectronic Al-doping on
GaN film, a new layer structure is proposed for a heterostructure
field effect transistor (HFET) including an isoelectronic Al-doped
channel. The electron mobility measured at 77 (300...
Based on investigating the effects of isoelectronic Al-doping on
GaN film, a new layer structure is proposed for a heterostructure
field effect transistor (HFET) including an isoelectronic Al-doped
channel. The electron mobility measured at 77 (300) K
significantly increased from 145 (130) cm$^2$/V$\cdot$s in the
undoped sample to 823 (440) cm$^2$/V$\cdot$s in the Al-doped
sample grown with a trimethylaluminum flow rate of 3 $\mu$mol
/min, while maintaining the background doping concentration below
$\sim$ 6 $\times$ 10$^{16}$ cm$^{-3}$. Two-dimensional electron
gas mobilities of 1690 and 9280 cm$^2$/Vs were measured for a
25-nm Al$_{0.3}$Ga$_{0.7}$N/1-nm AlN/70-nm Al-doped channel/GaN
heterostucture at 300 and 77 K, respectively. The improved results
are explained based on a decrease in the compensating acceptors or
other defects associated with the formation of screw dislocation
due to the incorporation of Al in the channel layer, plus a
decrease in the alloy disorder scattering in the heterostructure
based on introducing a binary thin AlN layer between the
Al$_{0.3}$Ga$_{0.7}$N and Al-doped channel layers.