The Formation of Low Resistivity Layers of -type in Heterostructure GaAlN/GaN

The Formation of Low Resistivity Layers of -type in Heterostructure GaAlN/GaN

When designing a functional heterostructure based on GaN, its manufacturing technology should allow to grow GaN and In GaN layers of n -type conductivity and GaN and Al GaN p -type conductivity. Specially unalloyed epitaxial layers GaN and In GaN have n type of conductivity with electron concentration ranging from 1∙10 to 1∙10 cm. In many works it is reliably established that uncontrolled donors are vacancies in the field of nitrogen atoms in the crystal lattice. These donors form small energy levels in the forbidden zone. The Ge and Si atoms in the GaN semiconductor are small donors. To create highly doped layers with a high concentration of electrons up to 1∙10cm, it is necessary to carry out a special doping with donor impurities during their cultivation. Impurities Si, O, C and structural defects, as a rule, form different neutral and electroactive complexes with each other, which, as studies show, easily disintegrate at temperatures T > 600 K. If there are currently no specific technological problems with obtaining n - layers, then obtaining p -GaN layers was the most difficult problem. It is shown that in the process of obtaining the method of MOCVD doped with GaN acceptors (with a large excess of NH), there is a thermodynamic possibility of localization of acceptors (A) due to the formation of a high concentration of neutral complexes ( A -H). It is established that the decrease in the concentration of the acceptor and, accordingly, hydrogen in the layers will reduce the localization of the acceptor in neutral complexes and simplify the technological task of obtaining low-resistance layers of the hole type of conductivity even at low concentrations of the acceptor. However, this will require the development of new technological methods, since such a task is directly related to the reduction in the epitaxy of GaN hydrogen content and «undesirable» impurities, such as Si, O and C. The optimal expenditure of CpMg, at which in the epitaxial layer the maximally possible concentration of Mg (6-8)·10 cm is achieved, is about 20-30 l/min. To achieve maximum values quantum yield annealing of heterostructures must be necessarily conducted in the temperature range (1063-1073 K).
  • Key words: gallium nitride, acceptors, neutral complexes, impurity activation
  • Bibliography link: Vigdorovich E.N. The formation of low resistivity layers of p-type in heterostructure Ga1–xAlxN/GaN. Proc. Univ. Electronics, 2019, vol. 24, no. 2, pp. 118–128. DOI: 10.24151/1561-5405-2019-24-2-118-128
Evgeny N. Vigdorovich
Moscow Technological University, Moscow, Russia
Share