BLUE 445 to 485nm Gallium Nitride and Indium Gallium Nitride on Al2O3

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Spectrum of a typical 470nm blue LED.

Opto Technology, part # OTL450A-1-1-46-D-2 (experimental/custom), 450nm GaN on SiC blue, NFS
Ms sweep Sox Finally after nearly a year of waiting, I have finally been able to see and experiment with an LED using one of Cree's new 450nm super blue narrow-band chips.
A sample of this LED was graciously loaned by a fan of the website and needs to be returned, so testing & pictures will be taken care of this weekend (October 7th and 8th 2000).

The delay was being caused by an illness called Pennant Fever, and I will be attending the Mariners home games - so if we sweep the series on Oct. 6th 2000, I will have plenty of time to take care of this LED on the 7th and 8th. :)
GO MARINERS!

OK... now that my baseball obsession is taking a break (we swept!), back to this neat little LED.

Opto Tech. LED This unusual LED comes in a TO-18 metal can and has what appears to be a PCX glass lens on the business end.
But it's what's inside the can that makes this LED interesting.

Let's start by going back about 8 or 9 months - let's call it mid to late 1999. Cree Corp. (formerly Cree Research) started coming out with these new short wavelengh, very narrow band blue LED chips. Until then, all blue LEDs had a relatively broad spectrum, with emission from red all the way to near violet, peaking at some intermediate blue wavelength (usually they range from 465 to 480nm).

This chip however, has almost NO visible emission outside the blue region and has a shorter peak wavelength (said to average 444.1nm in these samples) so it really is blue. Almost a violet blue in fact. Under most conditions, this LED has a violet tinge to it, which is apparent when the LED is operated next to some "ordinary" Nichia blue LEDs and even more so under the sickly yellow glow of a household incandescent lamp.

The dominant wavelength (different from the peak wavelength) of this sample is 451.4nm.

The power output of this LED hasn't been measured yet (I still need parts for my photometer), but appears to be in the 1.5 to 2.5 milliwatt range. This is consistent with Cree Corp's 450nm GaN on SiC LED chips of recent manufacture. This particular LED is packaged in a custom case, and LEDs using this chip are probably more likely to be found in ordinary plastic T1 3/4 "bullet" cases, the smaller T1 size case, and in SMD (surface mount) "chip-type" cases like those used inside cellular telephones to illuminate the buttons.

beam config beam config
These picture shows the relatively narrow, focused beam produced by the LED.
They are from two different samples of the same type & model number LED.

The TO-18 metal package is not normally used for visible LEDs (you are more likely to see IR and UV models in them) so don't go looking for these in your local electronic parts depot just yet. Eventually, they may start showing up in plastic cases but I don't see that happening for a good year or so. There just doesn't seem to be a big demand for LEDs of this wavelength yet, which is a shame, because they really are quite pretty.

UPDATE 04-27-01:
Kingbright is now selling LEDs that supposedly have similar characteristics to this one. I should know within the next couple of weeks just how close they are, and should also have some to offer on this website.


Opto Technology, part # OTL460A-1-1-46-D-2 (experimental/custom), 460nm GaN on SiC blue, NFS
This is the mate to the 450nm LED above. Packaged similarly, this one uses Cree's GaN on SiC 460nm narrowband chip; also a type I have not seen until now. This one is also on loan from the same website visitor, so it too will be taken care of over the weekend.

460nm 460nm
This LED has a beam configuration and case style similar to the Opto Technology 450nm model shown above.
The two most noticeable differences are that this is a 460nm (10nm longer wavelength) and it has a broader emission - I was able to detect emission clear into the red portion of the spectrum. Its output is a lighter, slightly whiter shade of blue - in some aspects, similar to Nichia's bluest bin sort but it isn't nearly as bright as a typical blue Nichia. The dominant wavelength of this guy is 460nm and the peak wavelength is 456nm.
While Nichia blue LEDs can exceed 7 milliwatts of optical output power, this one is probably closer to 2 or 3 milliwatts, which is right on track for Cree's 460nm chips.

The radiation pattern is consistent with LEDs packaged up in this fashion: a central hot spot, a weaker middle region, and an outer corona that is much weaker yet. So most of the LED's energy stays in the central area, and relatively little is wasted through refraction in the LED's glass lens. I suspect the chip/lens interface is a large air gap, so this isn't the most efficient design they could have chosen. However, this configuration isn't as wasteful as some other LEDs I've come across; where a substantial portion of the LED's energy is wasted as big ugly rings and other optical artifacts.

Its beam is a little on the narrow side to be truly useful for the most common applications such as diffuse panel indicators or backlighting. Because the LED chip image is focussed only an inch or so away from the lens though, a highly visible long-range indicator can be made using this LED without any additional treatment, but its overall viewing angle isn't as wide as one might desire for such an indicator.

However, you should note that this TO-18 metal can is uncommon for visible LEDs because it is custom, and like the 450nm version above, you are more likely to find this type of LED chip in a more ordinary looking (and efficient) plastic LED case, rather than in this metal can.



Radio Shack, part # 900-8005 (online and catalogue sales only), price $4.29 + $2.50 S&H
Until earlier this year, the only blue LED you could get from Radio Shack was based on early-mid 1990s technology - gallium nitride on a silicon carbide substrate. Although nice, they weren't particularly bright. Finally, the 21st century has come, and Radio Shack has finally decided to get with the times.

New RS blue Their latest offering is this brilliant blue LED using the most modern technology available to them. They buy these things from Nichia, the world leader in GaN LED technology. This piece is a Nichia LED, model number NSPB500S.
As you can see by the beam picture, this LED produces a bright, approximately 15 degree beam that is characteristic of Nichia's most popular blue LED.
The LED's brightness appears to be in the 3000mcd range, which is expected with an LED of this type and pedigree. When compared to other NSPB500 models, this one seems to be right down the middle as far as brightness is concerened.

Sadly, you cannot buy these in Radio Shack's retail stores yet, and can only get them through Radio Shack's website. Those who do not have internet access or a credit card may have to wait awhile before a nice bright Nichia blue LED shows up in a "brick and mortar" store near them.

Update: 10-08-00: A fan of the website has informed me that if you ask for Radio Shack's commercial catalogue, you can order them right at the counter by paying for the LED(s) in advance plus a $2.50 shipping fee and have them delivered right to your mailbox.
Most Radio Shack outlets should participate in this; however in some areas, certain outlets may or may not.

Care and Feeding: This LED would appreciate being fed 3.4 to 3.8 volts DC at 20 milliamps, and would thank you to the stars if you did not hook it up backwards. Like most LEDs using this new technology, connecting them backwards is very often fatal to them.
If you're feeling adventurous, you can run 30mA continuous current through them, although you need to be sure the LED is well-ventilated and kept cool if you do that.



International System Processing (ISP), part # IWV-UB51A1T, replaces LEL-47GN52, $0.55
This is the upgraded blue LED from Korean manufacturer ISP. They had sent some LEDs last fall which were a bit unusual, both in die shape and beam configuration; and they seemed a bit weak for the technology available. This is their upgraded blue.

Their previous model had a very narrow beam consisting of a long rectangle with notches at the end. This one has a more typical beam pattern, consisting of a ring surrounding a brighter central patch.


Beam photograph of the LED. Typical spot + ring configuration.
Intensity was measured at 2700mcd at beam center.


For the record, the spec sheet that came with these states the following:
Typical luminance: 2000mcd
Minimum luminance: 1500mcd
Wavelength: 470nm
Spectral line halfwidth: 26nm

This particular sample appears to have a wavelength close to the published value - just by eyeballing it I'd say between 469 and 472nm.
Brightness appears to be near the upper end of the range, so I received one of their better samples.
The beam isn't really suitable for things like flashlights, but these would be useful for indicators, marker lights, warning lights (like for bicycle/auto fixtures) and for general purpose panel & high ambient indicators.

Care & Feeding:
Like most GaN blue LEDs, these require 3.2 to 3.4 volts at 20mA. They can be run at 30mA continuously if active cooling is provided, and pulsed very briefly to 100mA.



International System Processing (ISP), part #LEL-47GN32, <$0.55
This offering from Korean manufacturer ISP is their blue LED in a 3mm (T1) size.
Rated at 360mcd, I can't say this is the brightest blue LED I've ever seen. But it is still bright enough to be seen in broad daylight, giving it some usefullness as a high ambient panel indicator and as a general purpose indicator for virtually any application needing one.

This LED produces a fairly wide, slightly uneven beam that is characteristic of many LEDs in T1 packages.
The beam photograph shows this LED produces a beam with an odd, eccentric dark region in it.

Unlike the larger model detailed directly above, there were some obvious color variations in the samples I was sent.
Some of the bluest specimens appeared to be close to the 465nm minimum wavelength rating, while one of them was clearly near the upper 478nm end, as evidenced by its very turquoise-tinted bright blue color. It wasn't the deep, pure blue found in the others.

These are normal manufacturing variations, and are nothing to be concerned about. ISP probably has the capability to sort widely differing colors into grouped bins of similar colors, much like Nichia does. That way, customers who require LEDs of a consistent color would be assured of getting just that.

Care and Feeding: For optimum LED comfort, feed this one 3.5 to 4.0 volts DC at 20mA. They can be driven at 30mA if you can avoid a temperature buildup (such as having several in a small, enclosed space) and can also be pulsed at even higher currents if you keep your pulses short.



B.G. Micro, part # LED1057, $2.95 apiece.
Several samples of this LED from two different experimenters have recently shown up. Now I can stage a "shootout" between the various pieces.
For starters, all appear to be Nichia NSPB500S 5mm blue LEDs with a clear case.

Sample #1 and #2 were purchased at the same time from the same lot; sample #3 was purchased by somebody else some weeks later.

Sample #1 (labelled as second brightest of a tested lot) and sample #2 (labelled as worse than average) were tested first.
Sample #1 is definitely, undoubtedly brighter than most other blue LEDs tested to date - and clearly outshines #2 by a good margin.
However, Sample #3 (in original packaging, simply labelled LED1057) slightly outshines them all when run seperately or when run with only one other LED sharing a 20mA current-limited power source.

When all three were hooked up at once, sample #1 and sample #3 were fairly close in brightness, with sample #1 being a slightly deeper shade of blue. Sample #2 was less than half as bright as #1 and #3.

This teaches us one thing: when ordering from B.G. Micro (and undoubtedly other surplus outlets as well), you can't always expect to receive LEDs of the same color or brightness, despite ordering using the identical part number.

The only way to get LEDs of consistent brightness and color is to order directly from Nichia, specifying both color bin sort (A, B, C, and sometimes D) and brightness (lot numbers ending in Q, R, S, and T - with T being the brightest). OEMs (original equipment manufacturers) often have first pick of both bin sorts and lot numbers, so you may or may not be entirely successful if you order as an individual rather than as a company or corporation.
Nichia also charges $8 apiece (!) for small quantities - so ordering from B.G. Micro and other parts stores will save you a lot of money despite the possiblilty of an occasional "dud" showing up in your bag.



(Labelled as) Nichia NSPB500S, chip date 02/1998 (obsolete)
This rather ordinary looking LED is actually quite confusing, and is very likely a museum piece.
early Nichia When you first fire one of these up, the color strikes you as being a little "off". Sure, it's blue, but not anything like Nichia's current production of blue LEDs. It is a somewhat whitish electric blue at normal currents (around 20mA in this case). But when current is lowered, things change. This LED turns distinctly aqua, then finally a dull brownish-green at sub-mA currents. Not even the early Panasonic model shifts this much.
It also shows a nearly continuous spectrum from mid-red to violet, a spectrum more like that early Panasonic multiple well model outlined just below. If this is indeed a genuine SQW (single quantum well) LED, it must be one of the very first ever produced.

The LED's chemistry is gallium nitride, and is functionally identical to its more modern (and much brighter) cousins you can buy almost anywhere.

For its museum value, if the original Silicon Carbide LEDs were the spark to the blue LED revolution, then this LED was the gas can.

Care and Feeding: Like most LEDs using this technology, feed it 3.4 to 3.8 volts at 20mA continuous. If this LED turns out to be an early multiple well model, you can spank it just so and get it to shoot pulses of UVA radiation! (see the LED directly below).



Panasonic 450nm Broadband (older multiple quantum well type), availability unknown, possibly going obsolete
Can you confuse two entirely different chemistries of LEDs with one another? Maybe you can, if you pick this guy out of your parts bag along with an original Silicon Carbide model. At lower currents, you can very easily confuse the two - but jack up the current a little and the difference will become quite clear.

When fed with currents over a few mA, this LED will become far brighter than any commonly available SiC model. Presented in a standard clear T1 3/4 case, this was the first truely ultra-bright blue LED type available. Nichia made these kind first, but other manufactures like Panasonic got into the blue LED racket not long afterwards. The chemistry is gallium nitride, with a multiple quantum well (MQW) structure; that has to do with how they deposit the gallium nitride onto the substrate - a chip of artificial sapphire crystal in this case. The technical description of how they are made is quite a bit more detailed than this website was designed for; if you are interested in the finer points of quantum mechanics, atomic structure, and metal organic chemical vapor deposition, look up "nitride epitaxy" or "MOCVD" on a search engine sometime. :)

mqw blue
This LED shines a brilliant, whitish-blue light that which covers most of the visible spectrum. But since its spectrum runs higher in the shorter wavelengths, its light has an azure or brilliant sky blue appearance to it. At lower currents, the LED has a pale blue color that looks a lot like the original silicon carbide blue models from the early 1990s. At higher currents, it has a much greater brightness and has a higher peak around 450nm, which is why they are called 450nm blues. :)

Because it has such a broad spectrum, most common colors of sunglasses won't completely block or filter its light out, lending a certain usefullness to the LED for such things as aviation indicators, high ambient indicators, automotive dash indicators, marker or warning lights, and pocket flashlights.

So begs the question: how DO you tell these apart from silicon carbides in your parts bag?
Easy. Just look inside them. This LED has a larger square chip with two whiskers attached to its corners, the silicon carbide has smaller chip with a single whisker attaching in its center. If you end up with diffused case models, just hook them up together, and it'll be very easy to pick out the dim bulb - that will be the silicon carbide.

Another, less well-known way to tell these apart is to feed them microsecond bursts of high current; typically over 500 milliamps (half an amp). This LED will respond to the punishment by emitting a strong secondary spectral band centered around 383nm in the ULTRAVIOLET region of the spectrum, while an ordinary silicon carbide LED will just kind of sit there.

Don Klipstein tells you how to hack these into ultraviolet (blacklight) LEDs on his blacklight LED page.




Nichia America, model NSPBF50S (flat, clear case), $8 apiece
This LED is an uncommonly bright, clear blue model with a very wide angle beam of 110 degrees by 80 degrees.
One thing that was noticed fairly soon after testing, was that their color is a noticeably deeper shade of blue than another Nichia model, the NSPB500S, that will be outlined here in the near future. Since I don't possess any decent spectrographic equipment, I have to guess- but I'd say the wavelength is about 10nm shorter (bluer) than the 500S. The difference is evident - striking even - when you shine the LEDs side by side and compare their color on a white target.

UPDATE 01-13-00: Color variations among blue Nichia LEDs are a natual part of the manufacturing process, and are caused by slight variations in the amount of dopant that each chip receives and by slight variations in the quantum well structure.
I have learned, from a friend in the industry, that these inherent color variants are actually separated into three distinct "bin sorts", each containing blue LEDs tested & found to be of identical or near-identical wavelengths to other LEDs in that particular bin.
A similar procedure is probably also done to a percentage of Nichia's white models, so those requiring large quantities of LEDs with the same shade will be assured of receiving just that.

This LED is packaged in a small, flat case with a flat face; identical to the white model NSPWF50S outlined near the top of this page; and was probably intended for use as backlighting or in certain kinds of RGB video screens or scoreboards.

UPDATE 07-08-00:
I have tried several samples of this LED with the NEW chip (February 2000) and they're far brighter than these. I have also seen an LCD backlight panel which uses this model, and it is very bright and impressive. For more information on backlighting panels using LEDs, visit Lumitex Corp. (http://www.lumitex.com) and have a good look around. Very impressive stuff, all possible thanks to this type & model of LED.

UPDATE 04-27-01:
Nichia has been constantly improving all of their LEDs. Blue and green are now available in a new brightness rank "T", in addition to ranks Q, R, and S.
Rank "T" blue LEDs in the standard T1 3/4 package with 15 viewing angle should now exceed 4500mcd in brightness.

LEDsprofile
(Left): A pair of the flat LEDs...... (Right): The beam profile from them. Note the even, diffuse glow on the test target.




Nichia America, model NSPB500S (blue, older), $8 apiece
This is a bright blue LED in a clear, T1 3/4 case. This particular LED (and others I received from the same lot) have a slightly lighter or greener color than other Nichia blue models I have tried; this is due to variations in the manufacturing process that are sorted into bin colors - see the description of the LED immediately above to see how that works. This LED should be available in the deeper blue shades that the LED model above produces if you know what to ask for.
The ones tested here seem to run around 473nm; as opposed to the approximately 465nm output of other Nichia models I have tried.

I found this LED to be dimmer than other Nichia LEDs I've tested; this is primarily because it's an older model, and Nichia tends to improve its technology without changing part numbers to reflect the improvement. LEDs like this frequently end up on the surplus market where hobbiests and experimentors have ready access to them; while their newest, prime models go directly to OEMs (Original Equipment Manufacturers) for installation in new products.

This LED produces a reasonably well-defined 15 degree round beam with a visible "hot spot" and ring, surrounded by a weaker coronal zone. This is typical of many of the narrower-beam LEDs; although the beam shape isn't as well-defined as a particular turquoise Nichia model that is currently being tested. The color is quite pretty, and can be used anywhere you want a radiant, striking light blue LED to catch someone's eye.

When operated at lower currents, this LED picks up a slightly greener color; charactistic of what happens to most other nitride-based blues. A higher current results in a more whitish coloration; however as this is bad for the LEDs, this isn't something I'm willing to do for any length of time - I'm not a murderer, and I wouldn't appreciate having the nickname "The Elliot Bay LED Killer". ;)

Beam from NSPB500
Beam pattern for this blue LED.


All-Electronics part # LED-58 (Nichia NSPB520AS, older), $3.75 apiece / 10 for $30.00.
This is a brilliant blue 465-470m LED made by Nichia, although I've been told it's only about half as bright as some models which are being made today. It is their model NSPB520AS (revision A, with stopper) from a couple of years ago. But these are still by far the brightest blue LEDs I've seen to date. This LED is rated at around 290mcd brightness with a 45 degree beam, and generates 3mW of photonic energy.
The color is a much brighter, lighter looking blue than the Radio Shack or Electronic Goldmine blue models and really catches the eye.

I tried 4 of these blue ones first; then ended up with 9 more of them later. They all seem to be consistent with one another in both color and brightness, although one of them is just a fraction dimmer than all the others. It isn't even noticeable unless you're running them all together - then you can pick out the dim bulb. These LEDs run on 3.6 to 4.0 volts, and are rated for 30mA maximum current. You can pulse them up to 100mA for increased brightness, but your pulses have to be short or else you'll be buying a lot of these.

The color is a really vibrant brilliant blue, and is highly visible both day and night. They are useful for high ambient indicators, since they can easily be seen even in direct sunlight. This is also the kind of LED they use for the blue color in the new LED jumbo video boards; one of which was installed in Seattle's new Safeco Field in early 1999.

LED taillight array on a wheelchair
As shown in the picture, I installed most of these in a strip across the back of my motorized wheelchair for night visibility. They *really* light up the night, and people are very impressed with the LEDs when they see them.
If I could afford it, I'd buy a lot more of them. If you like blue LEDs, these are for you.


Beam pattern for NSPB520 blue LEDs. Note the nice wide beam that fills the whole target.




Toyoda Gosei, part # EL15E-3B, approx. $2
This is a fairly unusual LED, as LEDs go. It is in a sky-blue tinted transparent case, which has an oval or cat's eye shape to it. Nichia refers to the shape as "Super Oval".
Don Klipstein was kind enough to send several LEDs to me, and this is one of them.
TG cat eyes

This blue LED doesn't appear to be quite as bright as the All-Electronics model I tried; but at higher currents it's still quite literally blinding. The color seems similar under most conditions, but its most unique feature is its cat's eye lens shape. Instead of a round or square beam, this LED has a highly elliptical, slightly irregular beam. I'm not sure exactly what application these were originally made for, but they're nice to look at in any case. The tinted case knocks the red portion of the spectrum (weak already) down a little more, so under some conditions these may appear slightly, just slightly bluer than a similar LED in a clear case.

UPDATE 11-11: Using a slightly less sophisticated power supply, I'm finding that this LED appears somewhat brighter than originally reported. There was a malfunction in the power supply used to test this one originally, causing the LED to operate with a low duty cycle at high frequency; so it didn't look as bright. Using true DC, this LED is too bright to stare into at close range even at a nominal 17.6mA of current.



Toyoda Gosei, part # E1L53-3B, approx. $2
Here is another LED that was given to me. This is a more standard looking LED in a clear, T1 3/4 case. But when it's lit up, the color seems to be a lighter shade of blue than most other blue LEDs. I can't really describe the blue color, but it's like some greenish-cyan color is mixed in. Brightness is slightly less than the All-Electronics / Nichia model, but because it has a narrower 30 degree beam, it actually looks brighter when viewed from a distance.

It produces a nice, round even beam approximately 30 degrees wide; when shone at a distant target at night, a weak central hot-spot (brighter zone) becomes evident. Shining at a closer target produces virtually identical results; so this LED has a nice, consistent output you can count on every time.

TG blue

UPDATE 10-24-99: After a hundred or so hours, this LED seems to appear slightly greener than it did before, when placed alongside Nichia's blue (the All-Electronics model). It isn't much of a change, but it's noticeable if you look, especially if you pay attention to reflected light and not at the LED itself.

TG round LED
Beam pattern from this more standard looking blue LED.



WHITE 5500-6500K InGaN+phosphor 
ULTRAVIOLET 370-390nm GaN 
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