Growth by molecular beam epitaxy and electrical characterization of Si-doped zinc blende GaN films deposited on β-SiC coated (001) Si substrates

We report the electrical characteristics of heavily Si-doped zinc blende GaN epilayers deposited on β-SiC coated (001) Si substrates. The β-GaN films were grown by molecular beam epitaxy using a rf plasma discharge, nitrogen free-radical source, and the doping concentration in the films was controlled over the range 1.5×10¹⁸-3.0×10²⁰ cm^-3 by suitably adjusting the temperature of a Si effusion cell. We have found that Si incorporation in β-GaN results in a relatively deep donor level (∼62 meV below the conduction band edge at a carrier concentration at room temperature of 10¹⁸ cm^-3). Also, we present evidence of simultaneous high mobility conduction band conduction (dominant at high temperatures) and low mobility impurity band conduction (dominant at temperatures <70 K) in heavily doped (n_RT≳ 10¹⁹ cm^-3) material.