MOVPE growth, optical and electrical characterization of thick Mg-doped InGaN layers

A series of Mg-doped thick InGaN layers with different Cp2Mg flows were grown on n-type GaN layers. The Mg doping effect on optical and electrical properties of InGaN:Mg was investigated through capacitance–voltage (C–V) measurements and temperature-resolved photoluminescence (PL). After annealing, p-type conductivity with acceptor concentrations about 3.5×1018 cm−3 and 9.5×1017 cm−3 were observed for the samples doped with little Cp2Mg. With the highest Cp2Mg flow, an inversion from p-type to n-type was observed by analysis of a Mott–Schottky (M–S) plot. The inversion of conductivity type was accompanied by a disappearance of InGaN band-to-band PL emission. It should be noted that annealing led to a substantial reduction of this band intensity. Thus, too high Mg doping is found to cause a strong compensation of p-type conductivity by nonradiative defects of n-type as it is seen from C–V and PL measurements.

► Mg-doped thick In0.18Ga0.82N layers with different Cp2Mg flows were investigated.
► Acceptor concentration of 3.5×1018 cm−3 was found for InGaN doped with low Cp2Mg.
► An inversion of conductivity type was observed at high Cp2Mg flow.
► Mg AE of ∼160 meV and ∼80 meV were obtained for In0.18Ga0.82N and GaN respectively.