[labnetwork] metals in a III-V oxidation furnace

[Noah Clay]

Hi Kurt,

When I worked in industry, we oxidized GaAs/AlGaAs VCSELs before metal dep, converting a high Al-containing AlAs layer to Al-O-As.  The concern for us was Au diffusion beyond the device’s contact layers.  I do recall that Au and other metals that we used, by themselves, were stable at the oxidation temp of ~500C, especially when compared to gold’s melting point of ~1000C.  

Assuming that you don’t have another option for metal annealing, I suppose you have to consider that trace Au contamination will occur.  However, if it was deposited on the chamber walls, it is unlikely to vaporize at 500C during a subsequent oxidation run.  If a small fraction were to break free from the furnace walls, there would be minimal cross-section for diffusing back into your target oxidation layer (considering a high O2 concentration gradient that results in O2 diffusion much faster than Au).  

After gold annealing, you could mitigate the risk of trace Au diffusion by burning in your furnace at a relatively high temp (e.g., 750C, if your hardware permits) under O2 for a relatively long time (e.g., 4-6 hours) to recondition the furnace for oxidation.  My thinking here - with no data - is to promote Au migration towards the end of the tube, downstream from the hot zone or the device location during oxidation.  This assumes that Ar or some other gas was flowing during any Au annealing, so that contamination is not ubiquitous in the tube.

Good luck,
Noah

BTW, anyone who reads this needs to register immediately for UGIM: ugim.nano.upenn.edu

Sent from my iPhone

> On May 2, 2018, at 16:22, Kurt Kupcho <kurt.kupcho at wisc.edu> wrote:
> 
> Hi all
>  
> Are there any concerns with allowing gold or other metals into a III-V material oxidation furnace like there is with metals in a Si thermal oxidation furnace?
>  
> Thank you
>  
>  
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