ENHANCHEMENT OF IONTZATION EFFICIENCY OF ACCEPTORS BY THEIR EXCITED STATES IN HEAVILY DOPED P-TYPE GaN AND WIDE BANDGAP SEMICONDUCTORS

摘要

The temperature dependencies of the hole concentrations p(T) for heavily Mg-doped GaN, Al-implanted 4H-SiC and Al-doped 6H-SiC, and lightly Al-doped 6H-SiC are obtained from Hall-effect measurements. The density and energy levels (ΔE_A) of acceptors are determined by the graphical peak analysis method (free carrier concentration spectroscopy) from p(T). Since ΔE_A is deep, it is found that a distribution function including the influence of the excited states of acceptors is necessary to the analysis of p(T) for the heavily doped samples. Moreover, it is proved that the excited states enhance the ionization efficiency of acceptors in the heavily doped case.