University of Essex Nanofab

These pages provide an overview of the semiconductor device research and teaching nanofabrication facilities

Wet Chemical Etching

Selective Etchants for AlGaAs/GaAs Structures 

1)     HCl (conc.) etches AlGaAs when Al >= 60% but does not etch GaAs only removes the oxides of GaAs

2)     Ammonium hydroxide: Hydrogen Peroxide ratio1:19

        etch rate 10um/min Etches GaAs but not AlGaAs for Al% > 30%. A reliable etch stop is 100nm of AlGaAs where Al>50%

3)     Citric Acid: Hydrogen Peroxide ratio 10:1

        etch rate = 0.2um/min

        Selectivity for etching GaAs (roughly 100:1) over AlGaAs when Al = 30%

        Citric acid:di water = 1:2 weight (gms) to volume (ml) ratio

        J.Vac.Sci.Tech B8 1122 (1990), C.Juang et al

One useful etch for GaAs based structures has the ratio sulphuric acid:hydrogen peroxide:deionised water = 1:8:80

It has an etch rate of about 0.5 microns per minute in undoped GaAs; and has the particular virtue that the etched surface is flat at the base of the mesa.

J.Electrochem.Soc. 128 p874 (1981), D.W.Shaw


Etchants for InP

Photochemical etching of GaN

These pages are written & maintained by Adrian Boland-Thoms