Contactless characterisation of 2D-electrons in GaN/AlGaN HFETs

We report on properties of 2D carriers in an GaN/AlGaN heterojunction investigated by an optical method. This method consists of a cyclotron resonance (CR) experiment where optical absorption is measured under fixed magnetic fields up to 13 T. We introduce a theoretical approach that allows to interpret cyclotron resonance due to the thin 2D layer on the sapphire substrate. The presented contactless characterisation method gives access to some very important parameters of the bidimensional gas such as the carrier concentration, their mobility and their effective mass. (C) 1997 Elsevier Science S.A.