86 research outputs found
Heat capacity of -GaN: Isotope Effects
Until recently, the heat capacity of GaN had only been measured for
polycrystalline powder samples. Semiempirical as well as
\textit{first-principles} calculations have appeared within the past few years.
We present in this article measurements of the heat capacity of hexagonal
single crystals of GaN in the 20-1400K temperature range. We find that our data
deviate significantly from the literature values for polycrystalline materials.
The dependence of the heat capacity on the isotopic mass has also been
investigated recently for monatomic crystals such as diamond, silicon, and
germanium. Multi-atomic crystals are expected to exhibit a different dependence
of these heat capacities on the masses of each of the isotopes present. These
effects have not been investigated in the past. We also present
\textit{first-principles} calculations of the dependence of the heat capacities
of GaN, as a canonical binary material, on each of the Ga and N masses. We show
that they are indeed different, as expected from the fact that the Ga mass
affects mainly the acoustic, that of N the optic phonons. It is hoped that
these calculations will encourage experimental measurements of the dependence
of the heat capacity on isotopic masses in binary and more complex
semiconductors.Comment: 12 pages, 5 Figures, submitted to PR
Zeeman splittings of the 5D0–7F2 transitions of Eu3+ ions implanted into GaN
We report the magnetic field splittings of emission lines assigned to the 5D0–7F2 transitions of Eu3+ centres in GaN. The application of a magnetic field in the c-axis direction (B||c) leads to a splitting of the major lines at 621 nm, 622 nm and 622.8 nm into two components. The Zeeman splitting is linear with magnetic field up to 5 Tesla for each line. In contrast, a magnetic field applied in the growth plane (B┴c) does not influence the photoluminescence spectra. The estimated g-factors vary slightly from sample to sample with mean values of g|| ~2.8, ~1.5 and ~2.0 for the emission lines at 621 nm, 622 nm and 622.8 nm respectively
AlGaInN Laser Diode Technology for Systems Applications
Gallium Nitride (GaN) laser diodes fabricated from the AlGaInN material system is an emerging technology that allows laser diodes to be fabricated over a very wide wavelength range from u.v. to the visible, and is a key enabler for the development of new system applications such as (underwater and terrestrial) telecommunications, quantum technologies, display sources and medical instrumentation
Thermal stability of in-grown vacancy defects in GaN grown by hydride vapor phase epitaxy
We have used positron annihilation spectroscopy to study the thermal behavior of different native vacancy defects typical of freestanding GaN grown by hydride vapor phase epitaxy under high pressure annealing at different annealing temperatures. The results show that the VGa‐ON pairs dissociate and the Ga vacancies anneal out from the bulk of the material at temperatures 1500–1700K. A binding energy of Eb=1.6(4)eV can be determined for the pair. Thermal formation of Ga vacancies is observed at the annealing temperatures above 1700K, indicating that Ga vacancies are created thermally at the high growth temperature, but their ability to form complexes such as VGa‐ON determines the fraction of vacancy defects surviving the cooling down. The formation energy of the isolated Ga vacancy is experimentally determined.Peer reviewe
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