Collective investigations on two typical semi-insulating GaAs ingots

Due to its high potential technological interest, semi-insulating GaAs has been a material extensively studied for some years. Nevertheless the published results and conclusions are scattered ; comparisons between the various data in litterature are often very risky because of the diversified nature of samples and preparations and also of the diversity of experimental set up used. This paper reports a set of coherent experimental measurements performed on two typical ingots. The first one is grown by horizontal Bridgman method with Cr and Ga2O3 added in the melt ; the second one is grown (undoped) by liquid encapsulated (B2O3) Czochralski method. The numbered samples were analysed following various physical, optical or electrical technics by different laboratories. Results and conclusions reported here show a good consistancy. Chemical and crystalline homogeneity are especially studied ; the role of chromium doping is also discussed. It is hop ed that this work will help the understanding of GaAs.