Lastly, the sample is etched in the Plasmatherm model 770 Electron cyclotron

resonance (ECR) reactive ion etcher (RIE). Initially the reactor conditions are set

according to a known GaAs etch recipe for the Plasmatherm 770 using Cl2 gas and Ar gas

as follows:

 Chamber Pressure: 2 mTorr
 Heat Exchanger Temperature: 20C
 Cl2 Flow: 10 sccm
 Ar Flow: 20 sccm
 Microwave Power: 900 Watts
 RF Substrate Power: 30 Watts
 Etch Rate: -3000A/min

It was found that the above recipe was too harsh for the samples used, removing the gold

entirely from the substrate surface. Since the interface between the GaAs substrate and

gold is of critical interest, the recipe had to be adjusted. Conditions were then set to

encourage plasma etching while minimizing the potential for excessive damage to the

sample as had occurred with the initial recipe. Several new recipes were tested to ensure

that the sample was being etched. Those recipes are listed below for each sample in

Table 2.

Table 2. Etch recipes for each sample

 Sample # 2 3 5 Original
 Parameters j Recipe
 Pressure (mTorr) 10 5 5 2
 Temperature (C) 25 25 25 25
 Cl2 Flow (sccm) 10 10 10 10
 Ar Flow (sccm) 5 5 5 20
 Microwave Power (W) 100 100 100 900
 RF Power (W) 20 20 20 30
 Time (seconds) 90 60 90 90
 Note: Samples 1 and 6 were not etched.