In this paper, promising experimental results for the p-type electrical properties of carbon-doped (C-doped)
AlGaN are discussed. P-type conductivity was experimentally achieved in C-doped (0001) plane AlGaN layers
with from a small amount to 55% solid Al composition, but not in (0001) plane GaN. The maximum free hole
density (determined by van der Pauw geometry-Hall effect measurement) achieved for an AlGaN layer with 10%
solid Al composition was p= 3.2 x 1018 cm-3. The maximum net ionized acceptor densities (NIAD = (NA--ND+)),
which were determined by capacitance-voltage measurement, for AlGaN with 6, 10, 27, and 55% solid Al
compositions, were all in the range of (3-7) x 1018 cm-3. Moreover, the electrical activity of the carbon acceptors
was estimated to be 55-71% from the NIAD and secondary-ion microprobe mass spectrometry analysis data on
the carbon concentration. Activation energy of carbon acceptors was estimated to be 22-30 meV from this
electrical activity. On the other hand, optical property of C-doped AlGaN was compared with undoped AlGaN.
Then we found new emission, which related to carbon acceptors, at smaller energy side by 29-35 meV from band
edge-emission of the AlGaN. A p-n junction was also fabricated using the C-doped p-type AlGaN.
We investigated rolls of crystal-field split-off valence band (CH VB) in the deep-UV laser by measuring a
transverse-magnetic-field (TM)-mode polarization of lasing and spontaneous surface and edge emissions above and
below the lasing threshold from the AlGaN multiple-quantum-well (MQW) laser at 240.8 nm and the anisotropic optical
properties of c-plane AlxGa1-xN multiple quantum wells and m-plane AlxGa1-xN single layer. These results indicate that
CH VB plays an important role in (E//c) polarization and anisotropic emissions from AlxGa1-xN with x≧0.5.
GaN and their alloy systems have a potential for the application of optical devices operating in blue and ultraviolet spectral region. In this paper, the possibility of (BAlGa)N quaternary system lattice matched to (0001) 6H- SiC substrate is described for ultraviolet emitters in the view of bandgap energy, lattice-matching to substrates. The estimated bandgap energy of quaternary system is ranging from 3.9 eV to 6.1 eV. It is also discussed that the crystal growth of (BAlGa)N systems using metalorganic vapor phase epitaxy. The quaternary system lattice-matched to (0001) 6H- SiC have an advantage for the laser application operating in ultraviolet spectral region.
Conference Committee Involvement (1)
Gallium Nitride Materials and Devices III
21 January 2008 | San Jose, California, United States
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