Selective wet etching for InGaAs/InAlAs/InP heterostructure field-effect transistors

The etching characteristics of InAlAs, InGaAs, and InP in citric acid/H/sub 2/O/sub 2/ solutions, and their applications to the fabrication of InAlAs/InGaAs/InP MODFETs are reported. High selectivities of up to 500 and 187 were obtained for InGaAs over InP and InAlAs over InP, respectively. Selectivity values ranging from 2.5 to 25 were achieved for InGaAs over InAlAs with citric acid/H/sub 2/O/sub 2/ solution ratio from 10 to 1. The activation energies for these materials and the etch profiles for a InGaAs/InAlAs/InP MODFET structure are reported. Citric acid/H/sub 2/O/sub 2/ solutions of appropriate ratios have been applied to both mesa etching and gate recessing with good results. These solutions may also be extended to the fabrication of InAlAs/InGaAs and InP/InGaAs heterojunction bipolar transistors.<
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