New Toshiba Blue Laser

From: 	denbaars@engineering.ucsb.edu
Sent: 	Thursday, September 12, 1996 1:12PM

More news, yesterday Toshiba annouced they got a GaN laser, also on sapphire.
Attached is the email I got from my research friend at toshiba
Kazu Itaya.

"Toshiba Blue GaN Laser"
It was press-released yesterday in Japanese, and submitted to JJAP.

Abstract is:

 We demonstrated a room temperature pulsed operation  of nitride
based multi-quantum-well (MQW) laser diodes with a cleaved mirror facet on
conventional C-face sapphire substrate.  A cleavage was performed along
<11-20> direction of the sapphire
substrate, and the cleaved facet was analyzed through observation of atomic
force microscope (AFM) and theoretical calculation.  A single spectrum at
the wavelength of 417.5 nm with a full width at half-maximum of 0.15 nm was
obtained.  The threshold
current was 5.0 A, and the voltage for threshold was 20 V.

CW Blue Laser

From: "Max N. Yoder"  (by way of Eric S. Hellman)
Subject: CW blue laser

Steve DenBaars reports that Nichia has CW laser at -40C and runs
for 4 hours

Professor S. Sakai from Tokushima Univeristy said
S. Nakamura presented following data at recent
Oyo Butsuri Conference in Japan.

- 40 degreeC CW at 400 nm for 5 hours
Jth=4-10 kA/cm2
nth=1019
internal loss=50 cm-1
internal efficiency = 86 %
carrier lifetime=3 ns
files

Violet Laser

At the Optoelectronics and Communications COnference (OECC) in Chiba, Japan, (mid July) Shuji Nakamura reported that the duty cycle for the violet laser is now up to 50%. He says they expect CW Operation "soon".

Is this the same color as before? Maybe we should call it "Bluji".

Read Robert Feuerstein's report.

Bay Area Newspaper focuses on "New Semiconductors"

"The amount of research and effort has just gone ballistic" says Prof. James Harris. An excerpt from the San Jose Mercury News can be found at the Harris Group HomePage.

Lasers at Meijo University!

The Meijo team announced diode lasers operating at 376 and 402 nm at ISBLLED. You can read more about it, along with a report of Nichia's live demo of a laser, in Steve Denbaars' summary of the meeting.

First Nitride Laser on Spinel Reported

The Apr 8 issue of Applied Physics Letters reports the first GaN based laser grown on Spinel (MgAl2O4) substrates. The Nichia team used the same stucture (with 20 periods in the active layer) as for their lasers on sapphire, but grown on the (1 1 1) oriented face of spinel. Despite the fact that spinel can be cleaved, the lasers were made using polished facets. The threshold current of 8kA/cm2 was not so different from their other lasers. There are some pretty blue pictures in the paper.

First Cleaved Facet Nitride Laser Reported

The latest issue of Japanese Journal of Applied Physics reports the first GaN based laser with cleaved facets. This was realized by using the sapphire A-plane as the substrate material. Under room temperature pulsed operation the threshold current was 9.6 kA/cm2 with no post cleave mirror facet coating.

Discussion on Nichia Lasers Inaugurated

A discussion on the Nichia Laser has been inaugurated in the Journal's discussion section. The moderators are Prof. Steve Denbaars of UCSB and Prof. Jim Harris of Stanford University.

Nichia to Demo Laser at Chiba Meeting

Shuji Nakanura is planning to do a demonstration of a bluish-purple laser diode using an actual InGaN MQW laser diode at the Chiba Conference, March 3-5.

Nichia Shows Nitride Laser

At the Photonics West meeting in San Jose, Shuji Nakamura for the first time presented his blue laser results to the technical community. The MIJ-NSR summary of the meeting is available in the news section.

Here are some photos he showed at the meeting.

This is the laser below threshold. You can see everything lit up with spontaneous emission.

This is the laser above threshold. You can see the laser beam reflected on the sheet of paper, and the spontaneous emission is clearly reduced.

Thanks to Shuji Nakamura and Nichia Chemical Industries for permission to make these photos available.

In a paper published Jan. 15 in the Japanese Journal of Applied Physics, Shuji Nakamura and colleagues at Nichia Chemical Industries, Ltd. present the first electrically pumped III-nitride laser. Under pulsed conditions, the device produced 215 mW at a forward current of 2.3 A (34 V) at a wavelength of 417 nm. The differential quantum efficiency was 13% per facet and the threshold current density was 4 kA/cm2. Above the threshold current, an elliptical far-field pattern was observed.

The active region of the device consisted of a multi-quantum well structure of 26 periods of In0.2Ga0.8N(25 Å)/In0.05Ga0.95N(50 Å). The active layer is surrounded by GaN guiding layers and AlGaN cladding layers. A 0.1 micron In0.1Ga0.9N layer was grown on the sapphire substrate prior to deposition of the first AlGaN cladding layer to suppress the formation of cracks. The InGaN MQW structure was protected from thermal decomposition by growth of a 200 Å AlGaN capping layer prior to raising the temperature for growth of the GaN waveguide. The laser facets were formed by RIE etching with a chlorine plasma.

-Summary by C. Abernathy, 1/11/96

Date: Mon, 11 Dec 95 18:04:30 JST
From: Shuji Nakamura 
Subject: III-V Nitride based Laser Diode


Dear Colleagues


We have suceeded in fabricating III-V nitride based laser diodes for the 
first time. We will do press release on December 12, 1995. 
Also, in Japan,NHK will broadcast on  our laser diodes at noon and
night time by TV news on December 12, 1995.                              
I send this e-mail message for your notice.
If you want to know in detail, please read Japanese news papers on later than
December 12, 1995.
Also, read my paper which will appear on Jpn. J. Appl. Physics if you want to
know in deatail.


Shuji Nakamura
Nichia Chemical Industries Ltd.
According to page 7 of the Japan Times of Dec 13, "Nichia plans to develop a practical model in two years." Other than stating that the wavelength of the laser is 410nm, no further details are reported.
Page 15 of the Asahi Shimbun of Dec 13, reports that the blue laser will lead to increased storage density for CD's and DVD's, and reports that the Nichia's laser diode has 10 stacked layers of GaN etc.
Nikkan Kohgyo of 13 Dec 95, contained additional information that might be of interest. It mentioned the following.
  1. Wavelength - 410 nm
  2. Pulse width - 1 microsecond
  3. Duty cycle - 0.001
  4. Current Density - 4 kiloamps
  5. Maximum pulse power output - 10 milliwatts
If you have news to share on this or other topics related to nitride semiconductor research, please send mail to news@nsr.mij.mrs.org

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Thank you to R. Feuerstein, S. Nakamura, O. Hellman, T. Strite and J. Yakura for the above news items.

last updated Thursday, September 12, 1996 5:08:42 PM.

© 1996 The Materials Research Society
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