An irregular shard of a crystal wafer is set on a table, with two wire probes contacting it. Between the probes, a bright blue-purple light glows, illuminating the rest of the wafer.

Making LEDs In The Home Fab

August 23, 2026 by Aaron Beckendorf 24 Comments

Impressive as it most certainly is when an amateur fabricates a semiconductor, most of the projects we’ve seen are more demonstrations than workable chips. [Dr. Semiconductor], however, is going much further with his fabrication process, and is already working on a method to bond chips to printed circuit boards. It’s difficult to align a PCB with the pads on the underside of an opaque silicon wafer, however, so as a trial run he’s made and bonded some transparent LED chips.

The starting material for these chips is a gallium nitride (GaN) LED epiwafer, a stacked structure of n-doped GaN, an indium gallium nitride quantum well layer, and p-doped GaN grown on a sapphire substrate. When current passes through the structure, electrons from the n-doped layer and holes from the p-type layer recombine in the quantum well layer, emitting blue light. To make a functional LED from this, [Dr. Semiconductor] needed to make electrical contacts to both the n-type and p-type layers. Making the n-type contact required cutting through the p-type and quantum well layers.

This would normally be done with reactive ion etching in chlorine, but [Dr. Semiconductor] came up with a new process: a 355-nm ultraviolet etching laser causes GaN to break down into gallium and nitrogen, with the resulting cut being cleaned up by a potassium hydroxide etch. To deposit the contacts themselves, [Dr. Semiconductor] formed a photoresist mask, deposited metal (nickel, silver, and titanium) in a sputtering chamber, and used a developer solution to dissolve the mask and lift off the unwanted metal regions.

A square, purple PCB is shown under a microscope. The PCB has four vias surrounding a transparent chip, which has a blob of translucent yellow material on top of it. — The LED after bonding and phosphor application.

When [Dr. Semiconductor] applied current between the two contacts, the LED glowed bright blue. The next step was to mount it to a PCB; to do so, he first sliced the wafer into individual LED chips with the ultraviolet laser. He then electroplated indium bumps onto a printed circuit board, positioned the chip above these bumps, added some rosin flux, and melted the indium bumps. This soldered the chip to the board and let the board power the LED.

Like most commercial white LEDs, these were blue; most LED assemblies additionally include a phosphor layer which absorbs blue light and emits another color. To create a white LED, for example, [Dr. Semiconductor] mixed cerium-doped yttrium aluminium garnet phosphor powder with clear silicone and spread it over the LED. This absorbs some of the blue light and emits yellow light, and the resulting mixture of blue and yellow light looks white to human eyes.

We’ve previously covered some of the history of LEDs and the phosphors which make them useful. This seems to be the first inorganic LED we’ve seen, but we’ve also seen a few homemade OLEDs.

Thanks to [SpuriousIndices] for the tip!

The Undead Remote

July 28, 2018 by Brian Benchoff 30 Comments

In the very late 1990s, something amazing was invented. White LEDs. These magical pieces of semiconductors first became commercially available in 1996, and by the early 2000s, you could buy a single 5mm white LED for less than a dollar in quantity one. A year or two later, an astonishing product showed up on infomercials airing on basic cable at 2 a.m. It was a flashlight that never needed batteries. With a small white LED, a few coils wrapped around a tube, and a magnet, you could just shake this flashlight to charge it. It’s just what you needed for when the Y2K virus killed all electronics.

Of course, no one uses these flashlights now because they suck. The early white LEDs never put out enough light, and charging a flashlight by shaking it every twenty seconds is annoying. There is another technology that desperately needs a battery-less solution, though: remote controls. They hardly use any power at all. That’s exactly what [oneohm] did for his Hackaday Prize entry. He created the Undead Remote.

The dream of a battery-less remote control has been dead since your parents got rid of that old Zenith Space Command, but here it is. This is really just a shake flashlight, a diode rectifier, a large capacitor, and some glue. Shake the remote, and you can change the channel. Is it useful? Certainly. Does it look weird and is it slightly inconvenient? Also yes. But there you go. If you want an easy way to deal with batteries in your remote control, this is a solution.

Blue LED Streetlights Keeping You Awake?

October 7, 2016 by Elliot Williams 78 Comments

If you’ve played around with “white” LEDs, you already know that there’s no such thing. There’s warm white and cool white and any numbers of whites in-between. And when white LEDs were new, the bluer “cool white” variety were significantly more prevalent.

Enough US states have swapped out their old street lights with LEDs that it may be having a measurable effect on people and on the animals around us. This is the claim in a recent position paper by the American Medical Association’s Council on Science and Public Health. (Report as PDF.)

Science strongly suggests that heavy doses of light can keep people from falling asleep, and that brighter LED streetlamps may be making the problem worse. The AMA report goes a step further, and pins extra blame on the color of the light. Blue light apparently suppresses the production of melatonin which helps you sleep at night. And it’s not just humans whose circadian rhythms are getting messed up — the effects are seen throughout the animal kingdom.

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