Enhancement of Blue Emission from Mg-Doped GaN Using Remote Plasma Containing Atomic Hydrogen

Abstract

We have found for the first time that blue emission from Mg-doped GaN was greatly enhanced by remote plasma treatment (RPT) with plasma containing atomic hydrogen, in particular, water vapor plasma, at low temperatures of 300-400 C. The highest enhancing factor was twenty, achieved by water vapor RPT at 400 C for 30 min. The enhanced blue emission was stable up to 500 C, similarly to blue emission from as-grown samples, suggesting the same origin and mechanism. We have confirmed that the emission mechanism is donor-acceptor pair (DAP) recombination, and have concluded that RPT produces a hydrogen-related donor level at E c À 0:37 eV involved in the DAP emission.

Green luminescence in Mg-doped GaN

“…Since the BL band is commonly observed in GaN:Mg grown by MOCVD and rarely observed in the MBE-grown GaN:Mg [5], one may expect that the deep donor involved in the BL band contains hydrogen as a part of the defect. Such an assumption is supported by the annealing studies in H plasma, according to which the BL band is greatly enhanced by remote plasma treatment, with plasma containing atomic hydrogen [32].…”

“…It can be greatly enhanced by thermal annealing at temperatures 600-800°C [29]. The BL band is attributed to transitions from a deep donor (∼0.4 eV below the conduction band) to the shallow Mg Ga acceptor [5,18,[30][31][32][33]. Such an attribution explains a very large shift of the BL band with increasing excitation intensity (from ∼2.7 to ∼3.0 eV), along with other properties of this band [18].…”

Properties of the main Mg-related acceptors in GaN from optical and structural studies

“…noted and sometimes dominates the PL spectra. [10][11][12][13][14] We show such spectra in Fig. 5 for MOCVD grown samples, measured under different excitation conditions.…”

Point Defects in GaN

“…Since the BL Mg band is commonly observed in GaN:Mg grown by MOCVD and rarely observed in the MBE-grown GaN:Mg, one may expect that the deep donor involved in the BL Mg band contains hydrogen as a part of the defect. Such an assumption is supported by the annealing studies in H plasma, according to which the BL Mg band is greatly enhanced by remote plasma treatment, with plasma containing atomic hydrogen (Kamiura et al, 2005).…”

“…The blue band in GaN heavily doped with Mg is attributed to transitions from a deep donor ($0.4 eV below the conduction band) to the shallow Mg Ga acceptor (Kamiura et al, 2005;Kaufmann et al, 1999;Reshchikov et al, 1999). Such an attribution explains the very large shift of the blue band with increasing excitation intensity (from $2.7 to $3.0 eV), along with other properties of this band.…”