Search

It is recalled that electrical properties of GaAs thin layers grown by MOVPE can be comparable to those prepared by the chloride VPE process as far as power and low noise FET's are concerned. It is shown how a large capacity MOVPE reactor working at low pressure could be a serious competitor of the ion implantation techniques if we consider reliability between runs and homogeneity on the wafers. State of the art performance for both low noise and power FET's are reported. Though static characteristics pf power FET's are always consistent with the layers properties, anomalous behaviour of dynamic characteristics related to power FET's are occasionally observed. Tentative correlations between substrates, growth parameters and FET's microwave performances are given. Backgating effect is also discussed in terms of substrates and growth conditions.

A research and development programme has been launched at the Laboratoire Central de Recherche, to optimise the growth parameters for the production of high quality semi-insulating bulk gallium arsenide by the Liquid Encapsulation Czochralski (LEC) technique. Mono-crystals up to 3″ diameter, weighing up to 2.5 kg, have been grown and assessed for a range of crystal-growth parameters. A method of minimising the concentration of gallium inclusions within the bulk material is described. Finally, we discuss an alternative method of minimising arsenic loss, namely growth under a partial pressure of arsenic, and present preliminary thoughts on the concept of a ‘hot wall’ puller.

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.