Fabrication of microstructures in III–V semiconductors by proton beam writing

While the creation of microstructures in Si and GaAs by irradiation with high energy protons and helium ions and subsequent electrochemical etching has already been reported, the creation of microstructures in InP using this technique is investigated here for the first time. It is demonstrated that proton irradiation of Fe-doped semi-insulating InP(0 0 1) leads to an amplified material removal in the irradiated areas during electrochemical etching in an HF solution. By this way microstructures were produced using a 2.25 MeV proton beam focused down to ∼1 μm. The depth of the etched structures depends on the etching procedure. In addition, amplified etching of non-irradiated material encircled by closed irradiated patterns was observed. Furthermore, irradiation with helium ions leads to the formation of thin freestanding InP layers by simultaneous underetching as well as etching from the sample surface of the irradiated regions. In contrast to the semi-insulating material, the irradiation and electrochemical etching of n-type InP results in an amplified formation of porous material which partly leads to a complete removal of the material in the irradiated areas. A comparison between GaAs and InP concerning the dissolution characteristics shows mainly a similar behavior of the semi-insulating types of these semiconductors and of the n-type materials.