Investigation of the formation of the 2.8 eV luminescence band in p-type GaN:Mg

Abstract

The stability of defects present in GaN:Mg has been investigated using photoluminescence (PL) spectroscopy. The two dominant defect-related PL emission bands in p-type GaN were investigated, the blue band at 2.8 eV and the ultraviolet (UV) emission band at 3.27 eV. The intensity of the 3.27 eV PL band increases with increasing resistivity, whereas the 2.8 eV PL band intensity increases with a decrease in resistivity. The luminescence data is explained by a model whereby the concentration of luminescent centers depends on the Fermi level position. The shallow donor responsible for the UV band is attributed to hydrogen, whereas the deep donor defect responsible for the 2.8 eV band is attributed to a nitrogen vacancy complex.

Formation and dissociation of hydrogen-related defect centers in Mg-doped GaN

“…For the shallow acceptor with an optical binding energy of around 225 meV, Mg Ga [8,9] is the most promising candidate. Whereas possible candidates for the shallow donor (20-30 meV) are O [10], Si [11], H [12] and V N -H [13].…”

“…Si Ga and O N are believed to have a E threshold for the displacement of the Si (or O) atom of the same order of magnitude as that for Ga and therefore should not be affected by the electron beam [15]. Recently, H [12] and V N -H [13] were proposed to be the shallow donor level in MOVPE-grown Mg-doped GaN. However, isolated H is expected to be a deep donor showing a negative Ubehaviour [16].…”

“…The formation energy of these donors rapidly decreases as the Fermi-level approaches the valence band [13]. Likely candidates for deep donors in heavily Mg-doped GaN are V N [13], Mg-V N [4], V N -H [12], Mg i [22] and Mg N [22]. To study the impact of electron irradiation on heavily Mg-doped (compensated) GaN, temperature-dependent CL spectra were collected both in untreated and LEEBI (10 kV, 10 nA, 180 s) areas of the sample (Fig.…”

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

“…Shahedipour, et al, based on a study of the PL and the hole concentration dependence on the annealing temperature, concluded that a deep V N -H donor complex is responsible for the BL [93]. Suski, et al, have performed high-pressure experiments which indicate that the pressure dependence of the BL peak position is much smaller than that of the band-gap, and is thus unlikely to be associated with a CB or SD transition [94].…”

Defect assessment of Mg-doped GaN by beam injection techniques

“…Different models have been proposed to explain the so-called blue luminescence of Mg-doped GaN. This emission has been often attributed to a DAP transition involving a deep level, but there has been no consensus as to whether the deep defect is a deep donor 18,19 or a deep acceptor. 16 The temperature redshift of the blue GaN:Mg band observed in this work agrees with the proposed DAP nature of the emission.…”