Search for: All records

The Be-related ultraviolet luminescence (UVLBe) band with a maximum at about 3.38 eV in GaN:Be is caused by the shallowest acceptor in GaN with the /0 transition level at 0.113 eV above the valence band. The luminescent properties of this acceptor were studied in detail. First-principles calculations identify this acceptor as the BeGaONBeGa complex. These calculations also predict a deep level, at 0.34 eV above the valence band. However, we were not able to find evidence for this level in photoluminescence experiments. 

Abstract GaN is an important semiconductor for energy-efficient light-emitting devices. Hydrogen plays a crucial role in gallium nitride (GaN) growth and processing. It can form electrically neutral complexes with acceptors during growth, which significantly increases the acceptor incorporation. Post-growth annealing dissociates these complexes and is widely utilized for activating Mg acceptors and achieving conductive p-type GaN. In this work, we demonstrate that other acceptors, such as C and Be, also form complexes with hydrogen similar to Mg. The effect of thermal annealing of GaN on photoluminescence (PL) was investigated. In samples moderately doped with Be, the Be_Ga-related yellow luminescence (YL_Be) band intensity decreased by up to an order of magnitude after annealing in N₂ambient at temperaturesT_ann= 400 °C–900 °C. This was explained by the release of hydrogen from unknown traps and the passivation of the Be_Gaacceptors. A similar drop of PL intensity atT_ann= 350 °C–900 °C was observed for the C_N-related YL1 band in unintentionally C-doped GaN and also attributed to passivation of the C_Nacceptors by hydrogen released from unknown defects. In this case, the formation of the C_NH_icomplexes was confirmed by the observation of the rising BL2 band associated with these complexes. AtT_ann> 900 °C, both the YL_Beand YL1 intensities were restored, which was explained by the removal of hydrogen from the samples. Experimental results were compared to the first principles calculations of complex dissociation and hydrogen diffusion paths in GaN. 

GaN samples were implanted with Be and annealed in different conditions in order to activate the shallow Be Ga acceptor. Low-temperature photoluminescence spectra were studied to find Be Ga -related defects in the implanted samples. A yellow band with a maximum at about 2.2 eV (the YL Be band) was observed in nearly all samples protected with an AlN cap during the annealing and in samples annealed under ultrahigh N 2 pressure. A green band with a maximum at 2.35 eV (the GL2 band), attributed to the nitrogen vacancy, was the dominant defect-related luminescence band in GaN samples annealed without a protective AlN layer. The ultraviolet luminescence (UVL Be ) band with a maximum at 3.38 eV attributed to the shallow Be Ga acceptor with the ionization energy of 0.113 eV appeared in implanted samples only after annealing at high temperatures and ultrahigh N 2 pressure. This is the first observation of the UVL Be band in Be-implanted GaN, indicating successful activation of the Be Ga acceptor.