news review
rhombus4
with the nitrogen deep acceptor in fact
Nitrogen cannot dope ZnO
occurs at much lower energies, at
wavelengths that have been all but ignored
in prior studies. When it comes to electrical
p-type, say UCSB researchers
measurements of acceptor-doped ZnO, the
researchers point out there are many
potential pitfalls, casting doubt on the p-
COMPUTATIONAL scientists at the However, independent verification of these type conductivity reports published to date.
University of California, Santa Barbara reports has been lacking, as have
(UCSB), have provided convincing evidence convincing demonstrations of pn junctions. “We are convinced that none of the
that nitrogen, which is widely believed to be substitutional acceptors (including Li, N, P,
a shallow acceptor in ZnO, is in fact a very The UCSB team, consisting of John Lyons, As, or Sb) will yield p-type conduction”
deep acceptor and cannot lead to p-type Anderson Janotti, and Professor Chris Van commented Project Scientist Anderson
conductivity. de Walle, performed calculations based on Janotti. “Interstitial doping still looks
the hybrid functional methodology. In an promising, although it may be difficult to
ZnO has been intensively pursued as an Applied Physics Letter published online it is accomplish in actual device fabrication.”
optoelectronic material, in hopes of reported that nitrogen acceptors have an
developing it into a wide-band-gap light ionization energy of 1.3 eV-much too large “Our finding that nitrogen is not a shallow
emitter that would compete with GaN-but to enable p-type doping. acceptor will come as a disappointment to
with the advantage that large single-crystal many who are excited about ZnO as an
substrates are commercially available. A They also address why the behaviour of optoelectronic material” said Van de Walle.
large part of the effort has been directed at nitrogen has been misinterpreted in so many “However, we hope it will contribute to
establishing p-type doping, which is very of the previous investigations. In optical resolving the conflicting results that have
challenging in wide-band-gap oxides in studies, the photoluminescence line most plagued the literature, and will refocus ZnO
general. Dozens of papers claiming commonly associated with nitrogen is now research efforts on the many exciting
observations of p-type conductivity have known to be caused by stacking faults. applications that do not require ambipolar
appeared in the scientific literature. Optical absorption and emission associated doping, such as transistors and sensors.”
RABOUTET
Iron-arsenic compounds sought
S.A.
Manufacturer of Molybdenum.
for quantum critical point
Components for MBE.
THE ABILITY of electrons to magnetic quantum critical point
Specialized Cleaning
conduct electricity with no can be found in these materials,
& Degassing available.
resistance is linked to their something which could prove
magnetic properties, new essential to the future
research has revealed. development of semiconductors.
A recently-discovered class of The researchers noted that high-
iron-based superconductors have temperature superconductors
undergone experiments by a team could be used to progress MRI
of Chinese and US physicists scanners, high-speed trains and
who discovered that the ability of electric generators.
electrons being able to conduct
electricity with no resistance is Mr Si stated: “The evidence from
specifically linked to their this study bolsters the hypothesis
magnetic properties. that high-temperature
superconductivity in the iron
Rice University revealed in a pnictides originates from
recent edition of Physical Review electronic magnetism.”
RABOUTET S.A.
Letters that close examination of
250 Av Louis Armand
several iron-arsenide compounds Low temp superconductivity is
Z.I Des Grand Prés
found that the strength of the caused by ionic vibrations. Last
F-74300 Cluses France
magnetic order was reduced year, Ames Laboratory research
when smaller phosphorus atoms revealed that iron-arsenide
Tél : 33 (0)4 50 98 15 18
were introduced and replaced the semiconductors’ ability to carry a
Fax : 33 (0)4 50 98 92 57
arsenic atoms. viable current could hold potential
E-mail :
info@raboutet.fr
for the future development of
http://www.raboutet.fr
Qimiao Si, a Rice physicist, said much sought after zero-resistance
this highlights evidence that a power transmission.
8
www.compoundsemiconductor.net January/February 2010
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87