Terahertz intersubband transition in GaN/AlGaN step quantum well

Wu, Feng; Tian, Wenjing; Yan, Weiyi; Zhang, J.; Sun, Shuaiqiang; Dai, Jiangnan; Fang, Yanyan; Wu, Zhihao; Chen, C. Q.

doi:10.1063/1.4802496

Cited by 35 publications

(14 citation statements)

References 24 publications

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“…Machhadani et al proposed a way to decrease the effect of the internal electric field by creating a 3‐layer well (step‐QW) with a virtually flat potential profile. This approach has been explored by Wu et al , who found that the creating this flat band structure is very sensitive to small changes in aluminum concentration and well depth. Despite these deficiencies, ISB transitions in the THz region have been reported , and a QW infrared photodetector has been demonstrated .…”

Section: Introductionmentioning

confidence: 99%

THz intersubband transitions in AlGaN/GaN multi‐quantum‐wells

Beeler

Bougerol

Bellet‐Amalaric

et al. 2014

Physica Status Solidi (a)

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Various designs of AlGaN/GaN structures displaying intersubband absorption in the THz spectral range are reported upon. Firstly, samples with 3‐layer quantum wells (step‐quantum‐wells) displaying far‐infrared intersubband absorption are presented. Theoretical analysis of the reproducibility issues associated to this architecture is done, and a more robust design based on 4‐layer quantum wells is proposed. Such a structure has been fabricated by plasma‐assisted molecular‐beam epitaxy using two Al effusion cells to produce three AlGaN concentrations, without growth interruptions. Samples have been structurally validated by transmission electron microscopy and X‐ray diffraction. Fourier transform infrared spectroscopy measurements show far‐infrared absorption of TM‐polarized light, which gets broader and deeper for increasing doping levels.

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Section: Introductionmentioning

confidence: 99%

THz intersubband transitions in AlGaN/GaN multi‐quantum‐wells

Beeler

Bougerol

Bellet‐Amalaric

et al. 2014

Physica Status Solidi (a)

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“…9,12 However, the transition energies of these step-wells are highly sensitive to structural parameters. 13,14 Moreover, the additional layers significantly increase the complexity of design and growth of practical devices. The challenges of the built-in polarization fields can be circumvented by utilizing non-polar nitride heterostructures.…”

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confidence: 99%

Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells

Edmunds

Shao

Shirazi-HD

et al. 2014

Applied Physics Letters

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We demonstrate THz intersubband absorption (15.6-26.1 meV) in m-plane AlGaN/GaN quantum wells. We find a trend of decreasing peak energy with increasing quantum well width, in agreement with theoretical expectations. However, a blue-shift of the transition energy of up to 14 meV was observed relative to the calculated values. This blue-shift is shown to decrease with decreasing charge density and is therefore attributed to many-body effects. Furthermore, a ∼40% reduction in the linewidth (from roughly 8 to 5 meV) was obtained by reducing the total sheet density and inserting undoped AlGaN layers that separate the wavefunctions from the ionized impurities in the barriers.PACS numbers: 78.67. De, 78.66.Fd The terahertz (THz) spectral region has attracted attention due to potential applications in medical diagnostics, security screening and quality control. GaAs/AlGaAs quantum cascade lasers (QCLs) have already demonstrated potential as THz sources in the 1.2-5 THz range. 1-5 However, the operating range of GaAs QCLs is limited by the longitudinal optical (LO) phonon emission at 36 meV (8.7 THz). Fortunately, GaN-based QCLs have the potential to operate in this range due to the larger LO-phonon energy (90 meV).To date, most studies of intersubband transitions in the III-nitrides have utilized the polar c-plane orientation. 6-10 Spontaneous emission from c-plane AlGaN/GaN QCLs in the THz region has been reported, although full laser operation has remained elusive. 11 The built-in polarization fields in c-plane heterostructures place a lower limit on the transition energy, and the inherent asymmetry in the conduction band profile reduces the dipole moment at the larger well widths required for operation in the THz region. These limitations have been partially mitigated by the implementation of more complex step-well designs. 9,12 However, the transition energies of these step-wells are highly sensitive to structural parameters. 13,14 Moreover, the additional layers significantly increase the complexity of design and growth of practical devices. The challenges of the built-in polarization fields can be circumvented by utilizing non-polar nitride heterostructures. Non-polar nitride structures may be achieved using either the cubic phase or the m-plane orientation of the wurzite phase. Near-infrared intersubband absorption in the cubic AlGaN/GaN has been observed, 15 and m-plane oriented We have already demonstrated molecular beam epitaxy (MBE) growth of high-quality m-plane AlGaN/GaN superlattices. 17,18 In this study, the samples consist of 26 quantum wells (QWs) grown on free-standing m-plane

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“…For example, the effects of the intense laser field, indium composition and the well width on the Electron Raman Scattering of the strained InGaN/GaN quantum wells, considering which the spontaneous polarization fields caused by the crystal structure can produce a strong internal built-in electric field [24], the coupled quantum wells and the interaction between the interface related Rashba and Dresselhaus spin-orbit interaction [25], the influences of polarization and structure parameters on the intersubband transition frequency within terahertz range and oscillator strength in GaN/AlGaN step quantum well and other factors including doping location and concentration [15], the properties of AlGaN-based multi-quantumwells designed for intersubband optoelectronics in the THz spectral range. The authors studied the reproducibility issues associated to the current step-QW architecture [26], the intersubband transitions in III-nitride semiconductor [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…In particular, semiconductor step-quantum well and multiple quantum wells have aroused great interest because these systems allow the development of light sources such as light emitting diodes and laser diodes in a wide range of the electromagnetic spectrum from terahertz to ultraviolet and far-infrared [9][10][11][12][13][14], secure communication, genetic analysis, biomedical sensing, explosive and drug detection, security screening, industrial process control, and spectroscopic imaging for astronomy and space physics [15,16]. The structure of the step-quantum well and multiple quantum wells is capable of improving the photoluminescence efficiency due to quantum confinement effect.…”

Section: Introductionmentioning

confidence: 99%