Selective enhancement of blue electroluminescence from GaN:Tm

Abstract

Selective enhancement of electroluminescent emission from high-energy transitions in Tm-doped GaN has been observed to be a strong function of GaN growth temperature. GaN:Tm thin films have been grown by molecular beam epitaxy at temperatures from 100 to 700 °C. At low growth temperatures (100–200 °C) the low energy (infrared-801 nm) transition dominates, while at higher growth temperatures (400–700 °C) the high energy (blue-477 nm) transition dominates. For films grown at low temperatures the main emission excitation mechanism is impact excitation, while for films grown at higher temperatures (⩾600 °C) the main excitation mechanism appears to be lattice impact ionization followed by energy transfer to Tm ions.

Photoluminescence properties of in situ Tm-doped AlxGa1−xN

“…15 The PL was excited using the 250 nm ͑ϳ4.96 eV͒ output of an OPO system, which corresponds to above-gap pumping for Al x Ga 1Ϫx N samples with xр0.62. Similar to previous reports, 8,9 the visible PL from GaN:Tm is characterized by a broad band extending from ϳ400 to 600 nm and near-bandedge emission at ϳ367 nm. A weak blue PL line located at ϳ478 nm from the 1 G 4 → 3 H 6 transition of Tm 3ϩ is hardly observable.…”

“…8 One of the main challenges in using RE-doped GaN for full-color display applications is obtaining efficient blue emission. While dominant blue emission has been reported from GaN:Tm EL devices, 8,9 the overall device efficiency was significantly lower than results obtained for GaN:Eu ͑red͒ and GaN:Er ͑green͒. 2 For RE-doped AlN, red emission has also been reported from Eu, and green emission from Erand Tb-doped amorphous and crystalline films.…”

“…The infrared PL at ϳ803 nm is tentatively assigned to the intra-4 f transition 3 H 4 → 3 H 6 of Tm 3ϩ ions. 9 Changing from GaN:Tm to Al x Ga 1Ϫx N:Tm led to pronounced changes in the PL properties. Upon increasing Al content, the 478 nm PL line gained in intensity and was clearly observed.…”

The effect of growth temperature on the luminescence and structural properties of GaN:Tm films grown by gas-source MBE

“…Therefore, it is important to optimise the growth condition to achieve efficient blue light emission from GaN:Tm. It has been well established in the literature that the substrate temperature [5], stoichiometry of the host material [9] and RE incorporation during MBE growth [10] have significant effect on the RE 3+ -related emissions. In this paper we investigate the dependence of Tm-related emission on the substrate temperature during GaN growth, and establish correlations between the emission efficiency and the sample morphology, by using electron and atomic force microscopy (AFM) together with spatially resolved cathodoluminescence (CL).…”

“…Rare earth (RE)-doped GaN (GaN:RE), such as GaN:Eu [1], GaN:Er [2,3] and GaN:Tm [2,[4][5][6][7], has sparked considerable interest because the combination of the stable wide-gap semiconductor GaN with the sharp optical emission of RE ions could lead to important photonic applications. While strong blue electroluminescence (EL) has been obtained from GaN:Tm [4], blue PL from Tm-implanted [8] and molecular beam epitaxy (MBE)-doped GaN [7] compares poorly with green and red PL emissions from Eu 3+ -and Er 3+ -implanted [1][2][3] and MBE-doped samples [7].…”