PII: S0961-1290(00)90296-5


News Update 

First diamond UV emitter 
The Frontier Technology 
Laboratory (Yokohama, 
Japan) of the Corporate 
R&D Department of 
Tokyo Gas Co Ltd has de- 
veloped the first dia- 
mond UV light emitting 
device Upn. J Appl.Pbys. 
39 (15 June 2000) 
L604-6). 

Room-temperature 
operation by current-in- 
jection is at 235 nm, the 
shortest wavelength re- 
ported to date. This 
could potentially in- 
crease optical storage 
density and capacity to 
10 times that of red 650 
nm AlGaAs laser cur- 
rently used in DVDs and 

four times next-genera- 
tion 400 nm GaN blue 
lasers (e.g. 4.5 hours of 
high-density TV per 
DVD), as well as effi- 
ciently irradiating fluo- 
rescent illuminating 
materials. 

Grains of diamond are 
synthesised from isotopi- 
tally pure (12C) carbon 
powder (refmed from 
“lower-value-added” liq- 
uefied natural gas - main- 
1Y methane) under 
high-pressure (about 
50,000 atmospheres) and 
temperature (1,500”Q.A 
solvent-catalyst was used 
to reduce impurities 
(such as nitrogen) and 

White LED wins 
Discover award 
Fred Schubert, professor 
of electrical and 
computer engineering 
at Boston University’s 
Photonics Center, is 
among eight winners of 
the 11th AlNlUd 
DISCOVER Magazine 
Awards for Technological 
Innovation (presented 
by the Christopher 
Columbus Fellowship 
Foundation). 

Schubert’s Photon 
Recycling Semiconductor 
LED uses at least two 

different-wavelength light- 
emitting active regions 
combined to produce 
white light. Some blue 
light emitted from InGaN 
through the sapphire sub 
strate is reabsorbed by a 
second AlInGaP active re- 
gion (wafer bonded to the 
first) which re-emits it in 
the yelIow/omnge/red 
wavelength range. Alth- 
ough experimental effi- 
ciency so far is c 10 
lumens/Watt, theoretical 
efficiency is 300 h/W 

(vs 280 h/W for 
phosphor-based wh- 
ite LBDs). The active 
regions can also be 
changed to produce 
hundreds of different 
colours. Boston Uni- 
versity Bled a patent 
on the PRSLRD in 
June 1999. 
_U_ 
Tel: +16173534626 

lattice defects 
and hence in- 
crease emis- 
sion efficiency 
compared to 
previous cur- 
rent-injected 
emission of 
semiconduct- 
ing diamond 
(which yield- 
ed only longer 
wavelengths). 

Unlike conventional 
semiconductors, the 
emission is intrinsic 
through an intermediate 
state due to free excitons 
(an electron-hole pair 
bound by the Coulomb 
force and in a stable en- 

ergy state - even at room 
temperature in FTL’s dia- 
mond). The ’ 2C diamond 
also has record thermal 
conductivity. 
TokyoGasCoLtd 
Tel : +81-35400-7597 
Fax : +81-334327629 

Comnlete Growth PEDIGREES With Our Breeds of Eni-wafers 

Ill-Vs Review *Vol.13 No.4 2000 , 7