Making a 485nm diode lol :p

[HydroSean]

Since the 480-490nm diodes are somewhat of a unicorn nowadays I figured I'd go into research to make my own 485nm diode. I know the traditional 450nmish diode uses an InN-ZnN-GaN NIP junction which gives a bandgap of 2.75eV (=450nm). I was thinking if maybe we could switch out the GaN for TiO2, there would in fact be a 2.55eV bandgap which is 486nm! The only problem is that the TiO2 and InN may not have compatible crystal structures and this may doom the experiment. The InN and GaN crystal structures are both Wurtzite so it naturally makes sense but the TiO2 (anatase) is a tetragonal crystal structure. This means they may or may not be compatible in transferring energy through the p-n junction. What do you guys think?

 

[tomfire1735]

go for it!!


if you have the equipment,experience,money,.....

 

[ElectricPlasma]

Well damn, I hardly know what those tiny diodes look like yet alone how they work. Looks like you've got quite the project ahead of you, I wish you luck! Can't wait to see what you come up with.

 

[HydroSean]

Well damn, I hardly know what those tiny diodes look like yet alone how they work. Looks like you've got quite the project ahead of you, I wish you luck! Can't wait to see what you come up with.

They're basically just layers of different semiconductor alloys.

I am in the process of paying off my undergraduate debt from college and then I'm off to a Ph.D program which will most likely be specialized in semiconductors/crystal growth/surface chemistry. I figured I could get a headstart on this project because I think it is very applicable to RGB laser data projectors seeing as that we don't have a "true blue" laser diode. After all, the 2014 Nobel prize did go to the "true blue" LED for its applicability in televisions. I think its a great field to get into.

 

[H2Oxide]

They're basically just layers of different semiconductor alloys.

I am in the process of paying off my undergraduate debt from college and then I'm off to a Ph.D program which will most likely be specialized in semiconductors/crystal growth/surface chemistry. I figured I could get a headstart on this project because I think it is very applicable to RGB laser data projectors seeing as that we don't have a "true blue" laser diode. After all, the 2014 Nobel prize did go to the "true blue" LED for its applicability in televisions. I think its a great field to get into.

Do you have a semiconductor fabrication lab at your disposal? If you do, why not?

Also worth noting, InGaP diodes can emit around the 610nm wavelength.

EDIT: I wonder how hard it would be to build an epitaxy chamber?

 

[HydroSean]

Do you have a semiconductor fabrication lab at your disposal? If you do, why not?

Also worth noting, InGaP diodes can emit around the 610nm wavelength.

EDIT: I wonder how hard it would be to build an epitaxy chamber?

Haha that's a good one but sadly no I don't. My professor who I am good friends with runs the surface chemistry lab at my college and I bet he would help me in his down time. They grow crystals epitaxially as well but for solid state batteries instead of semiconductors. I bet I could get him to help me out. I'm just stuck at developing the process because I don't know if the slip plane between the two lattice structures is going to be strong enough to hold itself together

 

[RedCowboy]

Another trick they use is to introduce trash at the edges of the substrate to define the edges, but getting the crystals to grow where the materials don't want to is a big part of overcoming the green gap, green diodes are not as efficient, so the projectors use blue LD's to pump phosphors to make the green light.

We are seeing a green shift, such as the 08 is a 455nm vs the long time 445 workhorses and the 450nm 44, I think the 07 @ 465 is desired but the efficiency is lagging and possibly longevity???

If you could get 485 to grow it likely would not be very efficient and fragile, but that's what the goal is, to get closer to an efficient bright blue and green.

I would like to see a 500nm LD.

Do you have a way to grow the gain medium?

What environment is it grown in? Is it an oxygen deprived environment and do you think oxygen is removed from the can of our blue and green laser diodes?

----edit-----

Ok you need an epitaxy chamber.
I will have to read about that, I have wanted to make diodes for a while now but never have been serious about trying to start into it.

If it was simple we would be flooded with them, one day it will be, but lessons are yet to be learned and that's a matter of time and money......I have some time, LOL.

 

[HydroSean]

Efficiency and longevity are near the bottom of the list for me, I just want to get the diode to work in the first place, efficiency and longevity come later in development.

Maybe the 500nm is more applicable to the data projection, I didn't know that the data projectors had to use phosphors to achieve the desired wavelength, but I thought they already had the green diodes...strange. I could research to find the correct bandgap for the 500nm diode, but that would require a bandgap of 2.48eV. I will play around with the semiconductors and see what I can come up with and get back with you.

So the way I was going to go at growing the medium would be to purchase this and then to grow several layers on top of it like what they did in this image

in this article here, but instead of the GaN I would use a different substrate with a lower bandgap, therefore effectively increasing the wavelength and yes it would have to be all done with lateral epitaxial growth in a growth chamber that has a very hard vacuum and a very low mean free path.

 

[Chrisbee]

This is all WAY over my head! But very interesting nonetheless!
I really hope you can achieve something even remotely close to this.
Being able to develop a laser diode on a more independent level would be extremely cool! Especially if you were able to make several, to distribute/sell to a few people in a certain laser hobbyist community.

 

[Encap]

They're basically just layers of different semiconductor alloys.

I am in the process of paying off my undergraduate debt from college and then I'm off to a Ph.D program which will most likely be specialized in semiconductors/crystal growth/surface chemistry. I figured I could get a headstart on this project because I think it is very applicable to RGB laser data projectors seeing as that we don't have a "true blue" laser diode. After all, the 2014 Nobel prize did go to the "true blue" LED for its applicability in televisions. I think its a great field to get into.

Here is something from 2007 where 485nm laser diodes were made:

"AlInGaN based blue and blue-green LDs were investigated with regard to the characteristics of GaN semiconductor laser diodes. High power, single mode blue LDs with high COD level (~334mW under CW operation at 25°C, kink-free at 150mW) and long lifetime (~10000 hours under CW operation, 50mW 25°C) were achieved. No significant characteristic differences between blue LDs on LEO-GaN/sapphire and GaN substrate were observed. The blue-green LD which has the wavelength of 485 nm was successfully fabricated and demonstrated under CW operation 25°C, while it showed poor performances of LD characteristics compared to those of blue LDs. We believe that the poor performance of blue-green LDs were caused by the piezo-electric effect by lattice mismatch along C-axis of GaN, In fluctuation by lattice mismatch and In solubility limit in InGaN QWs and thermal annealing which was performed during the p-layer growth."

https://www.researchgate.net/publication/253397570_Recent_achievements_of_AlInGaN_based_laser_diodes_in_blue_and_green_wavelength_-_art_no_64730X

 

[H2Oxide]

Maybe you should try to make a diode with well-documented characteristics and structure first to see if it's even plausible for a hobbyist to actually make a diode. If it's a success then I say go all out and start experimenting!

Also, how do you plan on coating the ends of the diode?

 

[CurtisOliver]

I would also love to see if this is possible. I would be very impressed if you achieve what you want HydroSean
The thing that interests me though; if it is possible, then a bunch of hobbyists experimenting might actually help aid research. Good Luck!

 

[H2Oxide]

The thing that interests me though; if it is possible, then a bunch of hobbyists experimenting might actually help aid research. Good Luck!

Eh, probably not going to happen. HydroSean might be able to pull if off because he already has access to some equipment, whereas a normal hobbyist wouldn't.

Even if someone managed to find a way to build all of the equipment required, it would still be a massive investment. The vacuum requirements alone put this out of reach for most hobbyists.

And don't even get me started on pulling your own wafers...

 

[CurtisOliver]

Hobbyists can only dream
I have given making diodes from scratch thought in the past, but never known where to start.

 

[HydroSean]

Hobbyists can only dream
I have given making diodes from scratch thought in the past, but never known where to start.

University my friend, university is the key to starting research. I am looking into a doctorate program which will allow me to do this lol I should have my undergrad debt paid off by next May and will be able to start next August hopefully. In the mean time I will work with my undergrad professor on developing this

 

[styropyro]

University my friend, university is the key to starting research. I am looking into a doctorate program which will allow me to do this lol I should have my undergrad debt paid off by next May and will be able to start next August hopefully. In the mean time I will work with my undergrad professor on developing this

I'm glad to hear that you will be able to work on this in a lab! If you continue working there until you start grad school, you'll get a ton of good lab experience and will have the time to focus on experiments, rather than just classes.

As for your quest on growing 485nm diodes, I wish I had more input but I'm not very knowledgeable on much of the semiconductor stuff. Like others have stated you should try to first recreate a setup from literature and see what kind of results you get, and then start modify it and see what happens. It may be helpful to have a friend who does computational chemistry to run simulations of different possible mixtures/structures.