Characteristics of nitrogen-doped p-ZnO thin films and ZnO/ZnSe p-n heterojunctions grown on a ZnSe substrate

We investigate p-type doping in ZnO prepared by the method of radical beam gettering epitaxy using NO gas as the oxygen source and nitrogen dopant. A narrow (0 0 2) peak is observed in the x-ray diffraction spectra, which indicates that the N-doped ZnO films are oriented along the c-axis. Secondary ion mass spectroscopy measurements demonstrate that N is incorporated into a ZnO film with a concentration of about 2.5 x 10(19) cm(-3). The hole concentration of the N-doped p-ZnO films was between 1.4 x 10(17) and 7.2 x 10(17) cm(-3), and the hole mobility was 0.9-1.2 cm(2) V-1 s(-1) as demonstrated by Hall-effect measurements. The emission peak of 3.312 eV is observed in the photoluminescence spectra at 4.2 K of N-doped p-ZnO films, probably neutral acceptor bound excitons and the band of 3.24 eV, connected with a donor-acceptor pair recombination. The activation energy of the nitrogen acceptor was obtained by the temperature-dependent Hall-effect measurement, and is about 145 meV. The p-n heterojunctions ZnO/ZnSe were grown on the n-type ZnSe substrate, and have a turn-on voltage of about 3.5 V.