| Temperature dependence of electron concentration, mobility and resistivity of four GaN:Si layers. |
| ESR spectra of GaN:Si layers. |
| Integrals of UV photoluminescence emission at room temperature. The room temperature PL spectra of GaN:Si layers in the UV region are plotted in the insert. |
| The low temperature photoluminescence spectra of GaN:Si layers. (The room temperature electron concentrations are given below the sample names.) |