Photoluminescence spectroscopy of Mg-doped GaN

Abstract

We have grown Mg-doped GaN films by metalorganic chemical vapor deposition with various CP 2 Mg flow rates. After 750°C postgrowth annealing, p-type GaN films with carrier concentrations and mobilities about 2ϫ10 17 /cm 3 and 10 cm 2 /V s, respectively, have been achieved. A dominant photoluminescence ͑PL͒ line around 2.9 eV was observed at room temperature. By studying the dependence of PL on excitation density at 20 K, the emission line around 2.95 eV can be attributed to a donor-to-acceptor pair transition rather than to a conduction band-to-impurity transition involving the Mg-related deep level. We suggest that the DAP transition line is caused by a Mg related deep level at about 510 meV above the valence band. It is much deeper than the acceptor level at 250 meV commonly produced by the Mg dopants.

Cu Induced Optical Transitions in MOCVD Grown Cu Doped GaN

“…According to the literature, the yellow luminescence originates by native defects such as Ga vacancies [12] and this emission band vanishes when introducing p-type doping [13 ], confirming its assignment to the Ga vacancy. In spite of that, the yellow band persists when sample remains n-type or semi-insulating [13,14,15]. Therefore, considering the semi-insulating electrical properties of the selected sample series, with no major change in the yellow PL upon Cu incorporation, it can be suggest that the origin of the yellow luminescence band is most likely due to the native defect like Ga vacancies.…”

Selective excitation of the yellow and blue luminescence in n- and p-doped Gallium Nitride

“…The large difference between activation energies obtained through resonant vs. above band-gap excitation is reminiscent of the YL experiments discussed Chapter 2. However, it should perhaps be noted that at least one group has reported thermal quenching at much lower temperatures (a quenching of a factor of 50 in going from low T to 300 K) [96]. It is not clear, though, why the result of that group should differ so much with the results of two other groups, which reported a quenching beginning at much higher temperatures, and a total quenching of only a factor of 10 in going from low T to 300 K [63,76].…”

Thermally stable Nb and Nb/Au ohmic contacts to p-GaN

“…This indicates that the presence of the Au capping layer may play a role in improving the electrical property of the Nb/Au contacts. Sheu et al, 12 investigating the effects of thermal annealing on Ni/Au contacts on p-GaN, showed that Ga-Au compounds, such as GaAu and GaAu 2 which were formed during annealing, could influence the electrical properties of the contacts. Thus, similarly, the better I-V characteristic for the Nb/Au contact annealed at 850°C could be attributed to the formation of Ga-Au reaction products, as described in the discussion of the XRD and TEM results.…”