MOVPE growth of AlGaAs/GaAs and InGaP/GaAs structures on patterned GaAs substrates.

Abstract

Introduction. Overgrowth of GaAs patterned substrates by MOVPE with AlGaAs or InGaP layers is an important step infabrication of advanced semiconductor structures. This problem was studied by several authors in the past [1−5 ]. Influence of growth parameters on the layer morphology prepared on various patterns was reported in these papers.Significant dependence of the morphology on the growth temperature has been observed in general. This paper also studies MOVPE growth of AlGaAs and InGaP layers on patterned GaAs substrates. Thedifference between this work and the data from literature lies in the shape and size of our three−dimensionalpatterns. A pyramid patterns with height of about 10 micrometers and various slopes of sidewalls were overgrownin our experiments. The sidewalls were prepared as non−crystallographic layers, contrary to structures publishedby other authors. The main goal of this work was to prepare structures with sufficiently large sidewalls. They canserve as a base for novel devices exploiting properties of two−dimensional electron gas prepared at them.Experiments and results.Various types of patterns have been prepared on GaAs (001) substrates by unique etching method developed forthis purpose [7]. Technique of sacrificial layers was used for preparation of our pyramids. The structure with thinAlAs and about 2 micrometers thick GaAs layers were grown on GaAs substrates at first. Then a titanium film wasdeposited and structure defined by photolithography. Pyramids were formed by etching in H