The electrochemistry of InP in Br2/HBr solutions and its relevance to etching behaviour

Etch rate-potential curves of p-InP in HBr and Br2/HBr solutions in the dark and under illumination were correlated with current-potential curves. It was found that InP is etched via a "chemical" mechanism both by HBr and Br2. In aqueous HBr solutions InP is only etched at a significant rate at concentrations higher than 5 mol/l. The Br2 etchants contained 4.5M HBr; in this case HBr only serves to complex Br2 to Br-3. The etch rate in Br2/HBr solutions is mass-transport controlled at InP(001) and kinetically controlled at InP with the (111) In orientation. The macroscopically obtained results are consistent with the profiles etched at resist edges in InP. The electrochemistry of Br2 at p-InP under illumination reveals some interesting aspects with regard to the agreement between the etch rate and the Br2 reduction.