Electrical characterization of InAs thin films

It is known that parallel conduction as a result of surface and for interface charge accumulation significantly shields the bulk electrical properties of InAs thin films when characterized using Hall measurements. This parallel. conduction in InAs can be modeled by using the two-layer model of Nedoluha and Koch [Zeitschrift fur Physik 132, 608 (1952)]; where an InAs epilayer is treated as consisting of two conductors connected in parallel viz. a bulk and a surface layer. Here, this two-layer model is used to simulate Hall coefficient and conductivity data of InAs thin films ranging from strongly n-doped (n = 10(18) cm(-3)) to strongly p-doped (p similar to 10(19) cm(-3)) material. Conventional Hall approximations, i.e. those that assume uniform conduction from a single band, are then used to predict the apparent carrier concentration and mobility that will be determined from conventional Hall measurements, with the aim of illustrating the error of such a simplified analysis of InAs Hall data: Results show that, in addition to ignoring parallel conduction, the approximations of conventional Hall data analysis have a further inadequacy for p-type InAs, in that the high electron to hole mobility ratio in InAs is not taken into account. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.