White light emission from Er, Pr co-doped AlN films

Xiang Li; Xiaodan Wang; Hai Ma; Feifei Chen; Xionghui Zeng

doi:doi:10.3788/COL201917.111602

Chinese Optics Letters, 2019, 17 (11): 111602, Published Online: Sep. 12, 2019

White light emission from Er, Pr co-doped AlN films Download： 811次

论文大纲

Xiang Li ¹Xiaodan Wang ^1,*Hai Ma ¹Feifei Chen ¹Xionghui Zeng ^2,**

Author Affiliations

¹ Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009, China

² Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China

160.4760 Optical properties 160.5690 Rare-earth-doped materials 160.6000 Semiconductor materials

Abstract

In this work, Er-doped aluminum nitride (AlN), Pr-doped AlN, and Er, Pr co-doped AlN thin films were prepared by ion implantation. After annealing, the luminescence properties were investigated by cathodoluminescence. Some new and interesting phenomena were observed. The peak at 480 nm was observed only for Er-doped AlN. However, for Er, Pr co-doped AlN, it disappeared. At the same time, a new peak at 494 nm was observed, although it was not observed for Er-doped AlN or Pr-doped AlN before. Therefore, the energy transfer mechanism between Er³⁺ and Pr³⁺ in AlN thin films was investigated in detail. Through optimizing the dose ratio of Er³⁺ with respect to Pr³⁺, white light emission with an International Commission on Illumination chromaticity coordinate (0.332, 0.332) was obtained. This work may provide a new strategy for realizing white light emission based on nitride semiconductors.

Aluminum nitride (AlN) belongs to an atomic crystal with strong chemical bonds, so it is chemically inert in most environments. Meanwhile, AlN has potential applications in the optoelectronic field due to its direct band gap. Because of its large band gap ( $- 6.2 eV$ ), AlN is transparent in the wavelength range from the ultraviolet (UV) to the infrared (IR)^{[13" target="_self" style="display: inline;">–3]}. Owing to the above properties, AlN is a suitable host for rare earth (RE) ions.

For the past decades, great progress has been made in the field of RE-doped GaN materials^{[4–9" target="_self" style="display: inline;">–9]}. However, the investigations of RE-doped AlN are still in the primary stage. In fact, AlN belongs to the ${P6}_{3} mc$ space group and has the same crystal structure as GaN. The RE ions substitute Al ions sites with $C_{3 v}$ crystal symmetry during crystal growth^[1]. For RE ions, according to Laporte selective rule, the transitions of the $4 f$ shell accounting for emission are forbidden, but the selections are relaxed due to the mixture between odd state and couple state caused by the impact of crystal fields^[10].

Efforts on Er-doped AlN materials have been under way^[1,11,12]. Kallel et al. have grown Er-doped AlN thin film by using molecular beam epitaxy (MBE) and studied the spectral properties. The main emission peak is blue light; the authors also calculated the energy levels of Er by the crystal field theory. The results of the experiments are consistent with the calculation, which demonstrates that Er ions substitute the lattice sites of Al ions in AlN^[1]. For the Pr-doped AlN materials, some research works have been carried out^[13,14]. The optical properties of Pr-implanted AlN films grown by MBE have been reported by Lozykowski et al. Green light emission was observed from the films^[13].

Based on previous works mentioned above, if Er ions and Pr ions are co-doped into AlN film, the film may simultaneously emit green light and blue light under excitation and realize white light emission. However, until now, there have been no such reports. On the other hand, there are few reports about RE co-doped AlN or GaN, such as Er, Tm co-doped AlN^[15], Pr, Tm co-doped GaN^[16], Pr, Er, Tm co-doped GaN^[17], and Eu, Pr co-doped GaN and AlN^[18]. In this Letter, Er and Pr co-doped AlN films were prepared through ion implantation. The luminescence properties were measured by cathodoluminescence (CL) spectroscopy. The energy transfer mechanism between ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN thin films was investigated in detail. Through optimizing the dose ratio of ${Er}^{3 +}$ with respect to $\Pr^{3 +}$ , for the first time, to the best of our knowledge, white light emission with Commission Internationale De L′E′clairage (CIE) chromaticity coordinate (0.332, 0.332) was obtained from Er and Pr co-doped AlN films.

The 2 μm thick AlN films were grown by hydride vapor phase epitaxy (HVPE) on (0001) sapphire substrates. The growth details were reported elsewhere^[19]. Er, Pr ions were doped into AlN films through ion implantation with the energy of 200 keV. The implanting ion beam was inclined about 10° with respect to the normal of the AlN films for reducing the channeling effect. In the Er-doped AlN, the implantation dose is $1 \times 10^{14} at / {cm}^{2}$ (atoms per square centimeter) and $5 \times 10^{14} at / {cm}^{2}$ , respectively. In the Pr-doped AlN, the implantation dose is $1 \times 10^{14} at / {cm}^{2}$ , $5 \times 10^{14} at / {cm}^{2}$ , and $1 \times 10^{15} at / {cm}^{2}$ , respectively. In the Er, Pr co-doped AlN samples, the dose of ${Er}^{3 +}$ ions is kept at $1 \times 10^{14} at / {cm}^{2}$ , and the dose of $\Pr^{3 +}$ is $1 \times 10^{14} at / {cm}^{2}$ , $5 \times 10^{14} at / {cm}^{2}$ , and $1 \times 10^{15} at / {cm}^{2}$ , respectively. All of the implanted samples were annealed at 1050°C under a flow of $N_{2}$ at one atmospheric pressure. Luminescence properties were measured by a MonoCL3+ CL spectrometer installed on a Quanta400FEG field emission scanning electron microscope (SEM). The accelerating voltage is 5 kV, the grating is 1200 l/mm, and the slit width is 1 mm. All measurements were carried out at room temperature.

In our previous work, the luminescence properties of Er-doped AlN have been reported^[15]. The CIE chromaticity coordinate of emission light is (0.284, 0.272). Obviously, it is far from the standard white light coordinate (0.333, 0.333). Figure 1 shows the luminescence spectrum of $\Pr^{3 +}$ -implanted AlN with a dose of $5 \times 10^{14} at / {cm}^{2}$ after annealing at 1050°C. The luminescence peaks at 528, 657, and 675 nm belong to ${{}^{3}P}_{1} \to {{}^{3}H}_{5}$ , ${{}^{3}P}_{0} \to {{}^{3}F}_{2}$ , and ${{}^{3}P}_{0} \to {{}^{3}F}_{3}$ transitions of $\Pr^{3 +}$ , respectively. The broad peaks at 378 and 480 nm are related to oxygen impurity and Al vacancy, respectively^[15]. The CIE chromaticity coordinate of emission light is (0.300, 0.287).

CL spectrum of Pr3+-implanted AlN with a dose of 5×1014 at/cm2 after annealing at 1050°C. Inset is the dependence of the intensity of the 528 nm luminescence peak on the implantation dose.

Fig. 1. CL spectrum of $\Pr^{3 +}$ -implanted AlN with a dose of $5 \times 10^{14} at / {cm}^{2}$ after annealing at 1050°C. Inset is the dependence of the intensity of the 528 nm luminescence peak on the implantation dose.

下载图片查看所有图片

As shown in the inset of Fig. 1, the luminescence intensity of the peak at 528 nm is the highest when the implantation dose is $5 \times 10^{14} at / {cm}^{2}$ . The non-radiative recombination rate is determined from the distance between $\Pr^{3 +}$ ions and defects^[16]. When the implantation dose is as low as $1 \times 10^{14} at / {cm}^{2}$ , the distance between $\Pr^{3 +}$ ions and defects is also large, and then the non-radiative recombination rate is low. However, due to the low dose of $\Pr^{3 +}$ , the luminescence intensity is not the highest in this work. On the other hand, if the implantation dose is too high, such as $1 \times 10^{15} at / {cm}^{2}$ , then the non-radiative recombination rate is too high, as a result, the luminescence intensity decreases, as shown in the inset of Fig. 1. In this work, $5 \times 10^{14} at / {cm}^{2}$ may be the optimal dose for $\Pr^{3 +}$ -implanted AlN films.

Figure 2(a) shows the CL spectra of three ${Er}^{3 +}$ and $\Pr^{3 +}$ co-implanted AlN films with different dose ratios of ${Er}^{3 +}$ with respect to $\Pr^{3 +}$ . For all three samples, a peak at 494 nm was observed and attributed to the transition of ${{}^{3}P}_{0} \to {{}^{3}H}_{4}$ of $\Pr^{3 +}$ ^[20], which was not observed in the $\Pr^{3 +}$ -implanted AlN sample. On the other hand, with the increase of the Pr dose in Er, Pr co-implanted AlN, the luminescence peak at 480 nm, belonging to the transition of ${{}^{4}F}_{7 / 2} \to {{}^{4}I}_{15 / 2}$ of ${Er}^{3 +}$ , became weaker and weaker. Therefore, the energy transfer process labeled as ET1 in Fig. 2(b) between ${Er}^{3 +}$ and $\Pr^{3 +}$ is possible. Due to nearly equivalent energy gap between ${{}^{3}P}_{1} \to {{}^{3}H}_{4}$ of $\Pr^{3 +}$ and ${{}^{4}F}_{7 / 2} \to {{}^{4}I}_{15 / 2}$ of ${Er}^{3 +}$ , resonant energy transfer is possible. The electrons on the excited state ${{}^{4}F}_{7 / 2}$ are de-excited to the ground state ${{}^{4}I}_{15 / 2}$ through non-radiative relaxation, and the energy is transferred to $\Pr^{3 +}$ through resonant energy transfer. The electrons on the ground state ${{}^{3}H}_{4}$ of $\Pr^{3 +}$ are excited to the excited state ${{}^{3}P}_{1}$ and relaxed to the lower excited state ${{}^{3}P}_{0}$ ; then, the transition of ${}^{3}P 0 \to^{3} H_{4}$ corresponding to the 494 nm luminescence peak is observed, and the transition of ${{}^{4}F}_{7 / 2} \to {{}^{4}I}_{15 / 2}$ of ${Er}^{3 +}$ corresponding to the 480 nm luminescence peak nearly disappears.

CL spectra and energy transfer model of Er3+ and Pr3+ co-implanted AlN thin films with the different dose ratios of Pr3+ with respect to Er3+, where the dose of Er is kept as 1×1014 at/cm2. (a) CL spectra of Er3+ and Pr3+ co-implanted AlN. (b) Energy transfer model between Er3+ and Pr3+.

Fig. 2. CL spectra and energy transfer model of ${Er}^{3 +}$ and $\Pr^{3 +}$ co-implanted AlN thin films with the different dose ratios of $\Pr^{3 +}$ with respect to ${Er}^{3 +}$ , where the dose of Er is kept as $1 \times 10^{14} at / {cm}^{2}$ . (a) CL spectra of ${Er}^{3 +}$ and $\Pr^{3 +}$ co-implanted AlN. (b) Energy transfer model between ${Er}^{3 +}$ and $\Pr^{3 +}$ .

下载图片查看所有图片

The efficiency of the energy transfer is mainly determined from the average distance between RE ions^[13]. In this work, the average distance is related to the implantation dose of $\Pr^{3 +}$ and ${Er}^{3 +}$ . When both of the doses of ${Er}^{3 +}$ and $\Pr^{3 +}$ are $1 \times 10^{14} at / {cm}^{2}$ , the average distance between ${Er}^{3 +}$ and $\Pr^{3 +}$ is relatively large. Although the new luminescence peak at 494 nm of $\Pr^{3 +}$ appears, the luminescence peak at 480 nm of ${Er}^{3 +}$ can still be observed. With the increase of dose of $\Pr^{3 +}$ , the average distance between ${Er}^{3 +}$ and $\Pr^{3 +}$ decreases, which is favorable for the energy transfer process. Therefore, when the dose of $\Pr^{3 +}$ is $5 \times 10^{14} at / {cm}^{2}$ , the luminescence peak at 480 nm nearly disappears, and the intensity of luminescence peak at 528 nm increases.

Two more interesting phenomena were also observed. In Fig. 1, the peak luminescence intensity at 528 nm has maximum and minimum values when the $\Pr^{3 +}$ implantation dose is $5 \times 10^{14}$ and $1 \times 10^{15} at / {cm}^{2}$ , respectively. However, in Fig. 2, peak luminescence intensity at 528 nm is highest when the $\Pr^{3 +}$ implantation dose is $1 \times 10^{15} at / {cm}^{2}$ . In addition, according to our previous work^[15], compared with Er-doped AlN, the peak luminescence intensity at 410 nm belonging to the ${{}^{2}H}_{9 / 2}$ to ${{}^{4}I}_{15 / 2}$ transition of ${Er}^{3 +}$ is obviously decreased in Er, Pr co-implanted AlN. The energy difference between ${{}^{2}H}_{9 / 2}$ to ${{}^{4}I}_{15 / 2}$ of ${Er}^{3 +}$ and ${{}^{3}P}_{2}$ to ${{}^{3}H}_{4}$ of $\Pr^{3 +}$ is only about 150 meV. Considering the assistance of phonons in the AlN lattice^[21], the energy transfer process labeled as ET2 in Fig. 2(b) is possible. Then, the non-radiation transition from ${{}^{3}P}_{2}$ to ${{}^{3}P}_{1}$ of $\Pr^{3 +}$ is expected. Therefore, for Er, Pr co-implanted AlN, the peak luminescence intensity at 410 nm is decreased obviously, and, with the Pr dose increase, the peak luminescence intensity at 528 nm is enhanced significantly. Here, we also noticed that the intensity at 410 nm is not decreased monotonously. This phenomenon needs to be investigated further in the near future.

We also calculate the CIE chromaticity coordinate of emission light of Er, Pr co-implanted AlN films. The results are listed in Table 1.

Table 1. The CIE Chromaticity Coordinate of Er, Pr Co-implanted AlN Films

${Er}^{3 +} / \Pr^{3 +} (at / {cm}^{2})$	CIE X	CIE Y
$1 \times 10^{14} / 1 \times 10^{14}$	0.323	0.312
$1 \times 10^{14} / 5 \times 10^{14}$	0.332	0.332
$1 \times 10^{14} / 1 \times 10^{15}$	0.329	0.335

查看所有表

The CIE chromaticity coordinate of standard white light is (0.333, 0.333). Therefore, when the dose of ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN films is $1 \times 10^{14}$ and $5 \times 10^{14} at / {cm}^{2}$ , respectively, the emission light is nearly white light. Figure 3 is the CIE chromaticity diagram.

CIE chromaticity diagram of Er3+, Pr3+ co-doped AlN film. The doses of Er3+ and Pr3+ in AlN films are 1×1014 and 5×1014 at/cm2.

Fig. 3. CIE chromaticity diagram of ${Er}^{3 +}$ , $\Pr^{3 +}$ co-doped AlN film. The doses of ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN films are $1 \times 10^{14}$ and $5 \times 10^{14} at / {cm}^{2}$ .

下载图片查看所有图片

In conclusion, through co-implanting Er, Pr in AlN films, a new luminescence peak at 494 nm was observed and attributed to the transition of ${}^{3}P 0 \to^{3} H_{4}$ of $\Pr^{3 +}$ , which was not observed in Pr-implanted AlN films. At the same time, the luminescence peak at 480 nm belonging to the transition of ${{}^{4}F}_{7 / 2} \to {{}^{4}I}_{15 / 2}$ of ${Er}^{3 +}$ became weaker and weaker with the increase of the Pr dose. We concluded that there is an energy transfer between ${Er}^{3 +}$ and $\Pr^{3 +}$ ions. When the dose of ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN films is $1 \times 10^{14}$ and $5 \times 10^{14} at / {cm}^{2}$ , we obtained an ideal CIE chromaticity coordinate (0.332, 0.332). This work demonstrated a way for realizing white light emission in AlN films through co-doping RE ions.

References

[1] KallelT.KoubaaT.DammakM.WangJ.JadwisiencazkW. M., J. Luminesc.134, 893 (2013).JLUMA80022-2313

[2] YanG.ChenG.QiuF.ZhaoY., Acta. Photon. Sin.35, 221 (2006).

[3] LiC.RenX.WuH.ZhengR.ZhaoJ.OuyangD.DuC.YanP.RuanS., Chin. Opt. Lett.16, 043201 (2018).CJOEE31671-7694

[4] MoY.WangX.ZengX.GaoW.WangJ.XuK., J. Synth. Cryst.44, 1569 (2015).

[5] NishikawaA.KawasakiT.FurukawaN.TeraiY.FujiwaraY., Appl. Phys. Express2, 071004 (2009).APEPC41882-0778

[6] MoY.WangX.YangM.ZengX.WangJ.XuK., Phys. Status Solidi B Basic Solid State Phys.253, 515 (2016).

[7] HuangH.YanD.WangG.XieF.YangG.XiaoS.GuX., Chin. Opt. Lett.12, 092301 (2014).CJOEE31671-7694

[8] KangJ. S.YoonJ. A.YooS. I.KimJ. W.LeeB. M.YuH. H.MoonC. B.KimW. Y., Chin. Opt. Lett.13, 032301 (2015).CJOEE31671-7694

[9] WangX.MoY.ZengX.MaoH.WangJ.XuK., Chin. Opt. Lett.14, 051602 (2016).CJOEE31671-7694

[10] QiF.HuangF.WangT.LeiR.ZhangJ.XuS.ZhangL., Chin. Opt. Lett.15, 051604 (2017).CJOEE31671-7694

[11] RinnertH.HussainS. S.BrienV.LegrandJ.PigeatP., J. Luminesc.132, 2367 (2012).JLUMA80022-2313

[12] MaaboolM.AhmadI.AliG.MaazK., Opt. Mater.46, 601 (2015).OMATET0925-3467

[13] LozykowskiH. J.JadwisienczakW. M.BensaoulaA.MonteiroO., Microelectron. J.36, 453 (2005).MICEB90026-2692

[14] FialhoM.MagalhaesS.AlvesL. C.MarquesC.MaalejR.MonteiroT.LorenzK.AlvesE., Nucl. Instrum. Methods Phys. Res B.273, 149 (2012).

[15] WangX.YangM.ZengX.MoY.ZhangJ.WangJ.XuK., J. Alloy Compd.726, 209 (2017).JALCEU0925-8388

[16] WangX.MoY.YangM.ZengX.WangJ.XuK., Opt. Mater. Express.6, 1692 (2016).

[17] WangX.MoY.ZengX.WangJ.XuK., Mater. Chem. Phys.199, 567 (2017).MCHPDR0254-0584

[18] RodriguesJ.MirandaS. M. C.SantosN. F.NevesA. J.AlvesE.LorenzK.MonteiroT., Mater. Chem. Phys.134, 716 (2012).MCHPDR0254-0584

[19] SunM.ZhangJ.HuangJ.WangJ.XuK., J. Cryst. Growth436, 62 (2016).JCRGAE0022-0248

[20] MaqboolM.AhmadI.RichardsonH. H.KordeschM. E., Appl. Phys. Lett.91, 193511 (2007).APPLAB0003-6951

[21] KanekoM.KimotoT.SudaJ., AIP Adv. 7, 015105 (2017).AAIDBI2158-3226

Xiang Li, Xiaodan Wang, Hai Ma, Feifei Chen, Xionghui Zeng. White light emission from Er, Pr co-doped AlN films[J]. Chinese Optics Letters, 2019, 17(11): 111602.

White light emission from Er, Pr co-doped AlN films Download： 811次

Fig. 1. CL spectrum of $\Pr^{3 +}$ -implanted AlN with a dose of $5 \times 10^{14} at / {cm}^{2}$ after annealing at 1050°C. Inset is the dependence of the intensity of the 528 nm luminescence peak on the implantation dose.

Table 1. The CIE Chromaticity Coordinate of Er, Pr Co-implanted AlN Films

Fig. 3. CIE chromaticity diagram of ${Er}^{3 +}$ , $\Pr^{3 +}$ co-doped AlN film. The doses of ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN films are $1 \times 10^{14}$ and $5 \times 10^{14} at / {cm}^{2}$ .

关于本站 Cookie 的使用提示

全站搜索

White light emission from Er, Pr co-doped AlN films Download： 811次

Fig. 1. CL spectrum of Pr3+-implanted AlN with a dose of 5×1014 at/cm2 after annealing at 1050°C. Inset is the dependence of the intensity of the 528 nm luminescence peak on the implantation dose.

Fig. 2. CL spectra and energy transfer model of Er3+ and Pr3+ co-implanted AlN thin films with the different dose ratios of Pr3+ with respect to Er3+, where the dose of Er is kept as 1×1014 at/cm2. (a) CL spectra of Er3+ and Pr3+ co-implanted AlN. (b) Energy transfer model between Er3+ and Pr3+.

Table 1. The CIE Chromaticity Coordinate of Er, Pr Co-implanted AlN Films

Fig. 3. CIE chromaticity diagram of Er3+, Pr3+ co-doped AlN film. The doses of Er3+ and Pr3+ in AlN films are 1×1014 and 5×1014 at/cm2.

相关论文

相关资讯

关于本站 Cookie 的使用提示

全站搜索

Fig. 1. CL spectrum of $\Pr^{3 +}$ -implanted AlN with a dose of $5 \times 10^{14} at / {cm}^{2}$ after annealing at 1050°C. Inset is the dependence of the intensity of the 528 nm luminescence peak on the implantation dose.

Fig. 3. CIE chromaticity diagram of ${Er}^{3 +}$ , $\Pr^{3 +}$ co-doped AlN film. The doses of ${Er}^{3 +}$ and $\Pr^{3 +}$ in AlN films are $1 \times 10^{14}$ and $5 \times 10^{14} at / {cm}^{2}$ .