N-type tellurium doping and compensation in GaSb grown by organometallic vapor phase epitaxy

GaSb epitaxial layers are incorporated into a range of electronic and optoelectronic devices. Despite the technological importance of GaSb, doping and compensation processes are not completely understood, making additional studies of these processes beneficial. In this work, the dependence of free electron concentration on the tellurium atom concentration was quantified for n-type tellurium-doped GaSb epilayers grown by organometallic vapor phase epitaxy on GaSb and GaAs substrates with two different substrate misorientations. This dependence of electron concentration on tellurium atom concentration was sublinear and monotonic, but different for each substrate misorientation. This indicated that the distribution of tellurium between shallow donors and all other tellurium-containing species depended strongly on the tellurium atom concentration and was affected also by specific epilayer growth conditions. The observed dependence of tellurium and electron concentration on dopant precursor mole fraction during growth exhibited a dependence on substrate misorientation and substrate type. The tellurium doping efficiency and compensation ratio were estimated using a model that assumed all tellurium atoms were incorporated either as shallow donors or as gallium vacancy–gallium antisite–tellurium acceptor complexes. Within the framework of this model, the sublinear dependence of electron concentration on tellurium atom concentration was attributed to an increase in the fraction of total tellurium atoms being incorporated into acceptor complexes as the tellurium atom concentration increased. These results demonstrate that the dependence of the electron concentration on tellurium atom concentration can be distinguished readily between epilayers deposited under different controlled conditions. This capability potentially is useful for optimizing growth conditions.