dc.description.abstract | GaN, activation of Mg-doped GaN, Hall measurement and fabrication of
GaN n+-p junction. In addition, the device processing technologies were
also paid attention to investigate the low resistance ohmic contacts of
GaN. The current-voltage (I-V) characteristics were measured at room
temperature using an HP4145B semiconductor parameter analyzer.
The characteristics of multiple high dose Si implanted GaN were
studied. 28Si+ implantation into Mg-doped and unintentionally doped GaN,
followed by thermal annealing in N2, air, Oxygen ambiences has been
performed to achieve n+-GaN layers. We have successfully convert all
p-GaN to n type for annealing temperature from 750℃~1000℃. Multiple
implantations are used to form a uniform Si implanted region. The
implantation conditions (dose/energy) were 2’1015 cm-2/40 KeV, 5’1015
cm-2/100 KeV and 5’1015 cm-2/200 KeV. The carrier concentration of the
film changed from 3×1017 cm-3 ( p-type ) to 5×1019 cm-3 ( n-type, Sheet
carrier concentration ns =3×1015 cm-2 ) when the Si-implanted p-type
GaN was annealed in N2 ambience at 1000℃. The activation efficiency
of Si in Mg-doped GaN is 27%. Decrease the implantation dose to 8’1014
cm-2/40 KeV, 2’1015 cm-2/100 KeV and 2’1015 cm-2/200 KeV, the carrier
concentration of the film changed from 8×1016 cm-3 ( n-type ) to 4.2×
1019 cm-3 ( n-type, Sheet carrier concentration ns=2.5×1015 cm-2 ) when
the Si-implanted un-doped n-type GaN was annealed in N2 ambience at
1100℃. The activation efficiency of Si in un-doped GaN is as high as 53
﹪. In addition, specific contact resistance( rc ) of Ti/Al/Pt/Au ohmic
contacts to n+-GaN, which formed by 28Si+ implantation in p-type GaN,
were also evaluated by transmission line model( TLM ). The rc is as low
as 1.5×10-6 W-cm2 when the metal contact was annealed in N2 ambience
at 600℃. The specific contact resistance ( rc )of Indium tin Oxide(ITO)
as-deposited on n+-GaN which formed by 28Si+ implantation in p-type
GaN and annealing 1000℃ 15min and 30min were 2×10-4 U-㎝ 2 and 8
×10-5 U-㎝ 2 .
The as-grown material and these implanted samples were also
characterized by photoluminescence (PL) using a 10mW He-Cd Laser
(325nm) excitation source with the spectra taken at room temperature.
The PL spectra showed that no emission peaks of these implanted
samples, this may be attributed that surface damages and amorphized
structure of GaN by high dose (1.2E16 cm-2) 28Si+ implantation.
The activation of metal organic chemical vapor deposition-grown
Mg-doped GaN by N2 annealing has been investigated. P type
conductivity with a net acceptor concentration of 1×1018 cm-3 and a
mobility of 4 ㎝2/VS was obtained by annealing 750℃. Variable
temperature Hall measurement have revealed that activation energy of
Mg-acceptor was 109meV after 750℃ anneal.
Finally , the n+-p LED by 28Si+ implantation are fabricated and
characterized at room temperature(RT). The room temperature (RT)
current-voltage characteristic exhibits that a turn on voltage measured at
100iA was equal to 1.5V; the forward voltage measured at 20mA was
equal to 34V. The breakdown voltage measured at -10iA was equal to
-19V. The room temperature (RT) electroluminescence (EL) is dominated
by an emission at 415nm(2.98eV) with a linewidth of 80nm(600meV) at
injection current of 10~50mA. When the injection current increases up to
60mA~80mA, the emission is dominated by the peak at 385nm(3.22eV).
The EL intensity linearly increases with increasing injection current.
As mentioned above of n+-p junction, this supports the Hall effect
data for convert the p-GaN to n type conduction. | en_US |