Optimization and temperature dependence characteristics of low temperature In0.3Ga0.7As and In0.53Ga0.47As-In0.52Al0.48As semiconductor terahertz photoconductors

Recently, detailed characterisation of materials and evaluation of devices based on low temperature (LT) grown InGaAs-InAlAs and GaAs-based terahertz (THZ) photoconductors using the Molecular Beam Epitaxy (MBE) technique have been reported by our group. In this work, the characterisation is extended in order to study the growth reproducibility of the photoconductors and the temperature dependence of their transport properties. We show that the structural, optical and transport characteristics of a photoconductor can be optimised by growing the same structure under the same growing conditions but in different MBE systems. The Hall Effect measurements over the temperature range of 100 K–400 K revealed temperature independency of the mobility within a wide range, in which the concentration is changing with the temperature. The majority of carriers are found to be electrons even in the case of Be doped samples, which is attributed to the large density of excess As anti-site atoms. The transport properties of low temperature grown materials are presented for the first time and the behaviour is found to be different to those of conventional materials, which are grown under normal growth conditions.