The electrical properties of Zn doped InAs and InAsSb layers grown on semi-insulating GaAs by metal organic vapour phase epitaxy, using dimethyl zinc as the p-type dopant source, have been studied. The influence of dopant flow rate, V/III ratio and substrate orientation on the electrical properties of these InAs and InAs1−xSbx layers have been studied at a few appropriate growth temperatures. A promising group V source, tertiary butyl arsenic was used as an alternative to arsenic hydride in the case of InAs growth. The electrical properties of the InAs and InAs1−xSbx epitaxial layers were mainly studied by the Hall effect. However, surface accumulation in these materials results in deceptive Hall results being extracted. A two layer model (assuming the layer to consist of two parallel conducting paths viz. surface and bulk) has therefore been used to extract sensible transport properties. In addition, conventional Hall measurements ignores the high electron to hole mobility ratio in InAs and InAsSb leading to erroneous transport properties.

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.

The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAS is investigated. The electrical properties of Sn doped InAs films grown on semi-insulating GaAs substrates by MOVPE are extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that Sn concentrations can be controlled over 2 orders of magnitude. The Sn doped InAs layers exhibit carrier concentrations between 2.7 x 1017 and 4.7 x 1019 cm-3 with 77K mobilities ranging from 12000 to 1300 cm2/Vs. Furthermore, the influence of the variation of these parameters on the structural properties of InAs are also reported. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-type behaviour for p-type samples, especially at low acceptor concentrations. A two-layer model is presented which can potentially be used to separate the bulk semiconducting properties from those of the surface layer. We here apply this model to two materials, InAs and InAsSb, and extract their transport properties.