Electrochemical capacitance voltage profiling of the narrow band gap semiconductor InAs

InAs is a narrow band gap compound semiconductor with potential applications in infra-red detectors and high speed transistors. In order to facilitate device design using this material, it is essential that carrier concentration profiles be accurately known. Capacitance-voltage (CV) profiling is often employed for this purpose. Due to surface Fermi level pinning, it is difficult to form metal Schottky contacts to InAs layers, making conventional CV profiling difficult. Electrochemical CV (ECV) measurements have been successfully performed on InAs epilayers grown by molecular beam epitaxy on GaP. A solution of 0.2 M EDTA with 0.2M NaOH and 10-20% by volume of ethylenediamine acts both as an etchant and as a Schottky contact to InAs. The profiles obtained for undoped InAs layers were compared to Hall effect data, and showed good agreement. ECV profiling of thick layers with p- and n-type doped regions is also demonstrated.