Dear MEMS,

I am trying to create stripe lasers.i am evaporating Ti(300A)/Au(1200A) broad
area using e-beam on my sample. then, using S1813 to create the steps. The
purpose of the photoresist is to cover the areas where i don't want the etch to
etch the metal. my sample is p-GaAs/pAlGaAS/n-AlGaAs/n-GaAs.  i have been using
2 types of etch processing.

1) 3HCL:1HNO3:2H2O(DI) to etch the Au and then using HF to etch the Ti. My
photoresist holds to both etches for at least 3 min. On the surface of the
sample, i can see that the the etch creates black dots. I have noticed this
every time i use the Aqua Regia diluted etch. It seems that the etch bubbles
and creates these black dots on the sample surface.

2) using KI/I2 etch for gold and then using the HF to etch Ti. The etch rate on
this one is very slow, 8A/min. and as a result, my photoresist can't hold
against the etch because it will take me at least 15min to etch through the
gold.

Can someone suggest another etch that can be used with my process. the etch
should be ok with S1813 photoresist and that it should be ok with p-GaAs layer.
Because i don't want to etch trought the p-GaAs.

Need your help

Ali