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The structural and optical properties of GaSb/InGaAs type-II quantum dots grown on InP (100) substrate.

Shuhui Z, Lu W, Zhenwu S, Yanxiang C, Haitao T, Huaiju G, Haiqiang J, Wenxin W, Hong C, Liancheng Z - Nanoscale Res Lett (2012)

Bottom Line: Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed.Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev.This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China. lwang@iphy.ac.cn.

ABSTRACT
We have investigated the structural and optical properties of type-II GaSb/InGaAs quantum dots [QDs] grown on InP (100) substrate by molecular beam epitaxy. Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed. Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev. The low-energy peak blueshifted with increasing excitation power is identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II), and the high-energy peak is identified as the direct transition (type-I) of GaSb QDs. This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor.

No MeSH data available.


PL spectra and PL peak energies. (a) The low-temperature PL spectra of the sample measured under different pumping powers from 3 mW to 30 mW; (b) The PL peak energies obtained under different excitation powers and the fitting curve of the peak energies with the third root of the excitation power.
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Figure 3: PL spectra and PL peak energies. (a) The low-temperature PL spectra of the sample measured under different pumping powers from 3 mW to 30 mW; (b) The PL peak energies obtained under different excitation powers and the fitting curve of the peak energies with the third root of the excitation power.

Mentions: Figure 2 shows the PL spectra of four-ML QDs at 20 K with an excitation power of 3 mW. It is obvious that there are two peaks centered at 0.75eV and 0.76eV, respectively. For identifying these two peaks, low-temperature excitation power-dependent PL spectrum tests were carried out, and the results were shown in Figure 3a. Figure 3b shows the PL peak energies with various excitation powers. It is obvious that the low-energy peak blueshifts with the increasing excitation power, while the position of the high-energy peak is almost constant. The PL peak blueshifts with increasing excitation power is a special character of type-II heterostructures. The other supporting evidence of the type-II luminescence is the linear dependence of the PL peak energies over the third root of the excitation density [20]. The inset of Figure 3b shows the linear dependence of the PL peak energies and the third root of the excitation power. Many researchers attributed the high energy PL peak to the transition of the wetting layer [9,10,21]. In these references, there is a common point where the wetting layer peak blueshifts also with increasing excitation power (type-II). However, the high-energy peak in our work is almost independent of the excitation power which is a typical feature of the type-I band transition. Therefore, the interband transition of the GaSb QD would be the only proper origin of the high-energy peak. In the growth process of the sample, the InGaAs cap layer was doped with Si. Because the dope concentration was relatively high, the Fermi level of the InGaAs layer may possibly be higher than the bottom of the conduction band of GaSb QDs. In such circumstance, the light emission intensity of the GaSb QD could be stronger than the type II transition due to the stronger spatial confinement of carriers in the QD and the nature of the direct transition type I transition. It may be the reason that the PL intensity of the direct interband transition (type I) was strong as observed in the experiment. So, these two peaks are identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II) and the GaSb QDs direct interband transition (type-I) respectively, as shown in Figure 4a.


The structural and optical properties of GaSb/InGaAs type-II quantum dots grown on InP (100) substrate.

Shuhui Z, Lu W, Zhenwu S, Yanxiang C, Haitao T, Huaiju G, Haiqiang J, Wenxin W, Hong C, Liancheng Z - Nanoscale Res Lett (2012)

PL spectra and PL peak energies. (a) The low-temperature PL spectra of the sample measured under different pumping powers from 3 mW to 30 mW; (b) The PL peak energies obtained under different excitation powers and the fitting curve of the peak energies with the third root of the excitation power.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3278347&req=5

Figure 3: PL spectra and PL peak energies. (a) The low-temperature PL spectra of the sample measured under different pumping powers from 3 mW to 30 mW; (b) The PL peak energies obtained under different excitation powers and the fitting curve of the peak energies with the third root of the excitation power.
Mentions: Figure 2 shows the PL spectra of four-ML QDs at 20 K with an excitation power of 3 mW. It is obvious that there are two peaks centered at 0.75eV and 0.76eV, respectively. For identifying these two peaks, low-temperature excitation power-dependent PL spectrum tests were carried out, and the results were shown in Figure 3a. Figure 3b shows the PL peak energies with various excitation powers. It is obvious that the low-energy peak blueshifts with the increasing excitation power, while the position of the high-energy peak is almost constant. The PL peak blueshifts with increasing excitation power is a special character of type-II heterostructures. The other supporting evidence of the type-II luminescence is the linear dependence of the PL peak energies over the third root of the excitation density [20]. The inset of Figure 3b shows the linear dependence of the PL peak energies and the third root of the excitation power. Many researchers attributed the high energy PL peak to the transition of the wetting layer [9,10,21]. In these references, there is a common point where the wetting layer peak blueshifts also with increasing excitation power (type-II). However, the high-energy peak in our work is almost independent of the excitation power which is a typical feature of the type-I band transition. Therefore, the interband transition of the GaSb QD would be the only proper origin of the high-energy peak. In the growth process of the sample, the InGaAs cap layer was doped with Si. Because the dope concentration was relatively high, the Fermi level of the InGaAs layer may possibly be higher than the bottom of the conduction band of GaSb QDs. In such circumstance, the light emission intensity of the GaSb QD could be stronger than the type II transition due to the stronger spatial confinement of carriers in the QD and the nature of the direct transition type I transition. It may be the reason that the PL intensity of the direct interband transition (type I) was strong as observed in the experiment. So, these two peaks are identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II) and the GaSb QDs direct interband transition (type-I) respectively, as shown in Figure 4a.

Bottom Line: Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed.Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev.This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China. lwang@iphy.ac.cn.

ABSTRACT
We have investigated the structural and optical properties of type-II GaSb/InGaAs quantum dots [QDs] grown on InP (100) substrate by molecular beam epitaxy. Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed. Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev. The low-energy peak blueshifted with increasing excitation power is identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II), and the high-energy peak is identified as the direct transition (type-I) of GaSb QDs. This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor.

No MeSH data available.