Advanced Semiconductor Laboratory
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AlN:Be


By
Kuang-Hui Li

June 26, 2017 - Posted in Discussion
Could we replace Mg by Be as p-dopant for AlN (AlGaN)? The most common p-dopant for AlN is Mg by introducing Cp2Mg into MOCVD reactor. In theory, group II elements and transition metals could be p-dopant for III-nitride.The conductivity of AlN:Mg (AlGaN:Mg, high Al %) is low at room temperature due to high ionization energy. By Hall-measurement, the ionization energy of AlN:Mg, Ea, is above 500 meV. Hole concentration of AlN:Mg, p, can be roughly estimated by two assumptions: acceptor concentration, Na, is 1020 #/cm3 and the energy of electrons in valence band follow Maxwell-Boltzmann distribution, p = Na e-Ea/kT. The hole concentration is around 1011 #/cm3 at room temperature, which causes AlN:Mg an insulator.

DUV optoelectronic device needs a conductive p-type AlN (AlGaN) layer. There are several ways to improve the conductivity of p-AlN (p-AlGaN), e.g. Tunneling Junction (TJ), p-type AlGaN superlattice (SL), and p-type graded AlGaN layer.

AlN:Be has lower ionization energy compared to AlN:Mg, and the ionization energy is around 330 meV. The hole concentration is around 1014 #/cm3 by the same assumptions above, which improves 3 order of magnitudes compared to AlN:Mg. However, no research group is able to have a conductive AlN:Be (AlGaN:Be).

Reference
Appl. Phys. Lett. 93, 141104 (2008); doi: http://dx.doi.org/10.1063/1.2996977

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