Midinfrared intersubband absorption on AlGaN/GaN-based high-electron-mobility transistors

Hofstetter, Daniel; Diehl, Laurent; Faist, Jérôme; Schaff, William J.; Hwang, Jeonghyun; Eastman, L.F.; Zellweger, Christoph

doi:10.1063/1.1471569

Cited by 31 publications

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“…Intersubband absorption in such quantum wells has been observed in the spectral range up to the telecommunication wavelength of 1:55 m [17][18][19]. Recently, IS absorption was also observed in GaN=AlGaN-based high-electron-mobility transistors [20].In this Letter we show for the first time that linear and particularly nonlinear IS absorption spectra of electrons in a GaN=AlGaN heterostructure show a distinct vibrational progression due to strong polar coupling to optical phonons. In femtosecond two-color pump-probe experiments in the midinfrared we observe during the temporal overlap of pump and probe pulses sharp spectral holes on different vibronic transitions spectrally separated by the LO-phonon frequency.…”

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confidence: 99%

“…The piezoelectric field together with the heterointerface result in a deep triangular well shown in Published in Physical Review Letters 94, issue 037403, [1][2][3][4]2005 which should be used for any reference to this work Fig. 1(b) together with the calculated probability densities of the two lowest electron subbands n 1 and n 2 [20]. The stationary IS absorption spectrum (symbols) measured at a temperature of 300 K is plotted in Fig.…”

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Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

et al. 2005

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We present the first evidence for a distinct optical phonon progression in the linear and nonlinear intersubband absorption spectra of electrons in a GaN=Al 0:8 Ga 0:2 N heterostructure. Femtosecond twocolor pump-probe experiments in the midinfrared reveal spectral holes on different vibronic transitions separated by the LO-phonon frequency. These features wash out with a decay time of 80 fs due to spectral diffusion. The remaining nonlinear transmission changes decay with a time constant of 380 fs. All results observed are described by the independent boson model.The optical line shapes of electronic transitions in condensed matter reflect the ultrafast dynamics of the elementary excitations to which the electrons are coupled. Of particular interest for a broad range of phenomena is the coupling between electrons and nuclear motions, i.e., local vibrational modes and/or phonons.(i) Coupling to underdamped nuclear motions gives rise to spectrally distinct sidebands in electronic spectra [1]. In molecules, such an interaction with intramolecular modes underlies the vibronic structure of electronic absorption and emission bands, which are additionally broadened by dephasing and spectral diffusion processes originating from a coupling to (overdamped) motions of the fluctuating surroundings [2,3]. In crystalline solids with much more delocalized electronic wave functions and phonon modes, phonon sidebands of electronic transitions have been observed mainly for interband spectra of impurities [1], for quantum-dot-like structures [4][5][6][7][8], and through coherent phonon oscillations modulating the optical reflectivity [9,10].(ii) Electron-phonon coupling strongly influences the nonequilibrium dynamics of electrons, both in the quantum-kinetic [11] and in the incoherent scattering regimes [12]. Such phenomena occur on femtosecond to picosecond time scales and have been investigated extensively by ultrafast nonlinear spectroscopy.So far, the majority of investigations of electron-phonon coupling focused on interband transitions in solids. The influence of electron-phonon coupling on intraband transitions was mainly studied in the context of polaron physics [13,14]. Intraband transitions provide direct access to the nonequilibrium dynamics of electrons. Theoretical studies suggest a prominent role of electron-phonon coupling for the line shape of intraband (free-carrier) absorption and emission. So far, clear experimental signatures of electron-phonon coupling are missing for the line shape of intersubband (IS) transitions (dipole-allowed transitions between quantized conduction subbands [15]), although first theoretical studies predict such polaronic signatures [16].Because of their strong electron-phonon coupling, nanostructures made from strongly polar materials like group-III nitrides are promising systems for the occurrence of IS phonon sidebands. Because they have large conduction band discontinuities and thus allow IS transitions at short wavelengths, GaN=AlGaN multiple quantum wells have received much interes...

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Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

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“…We investigate a heterostructure grown by molecular beam epitaxy on a c-face sapphire substrate originally developed as a high-electron-mobility transistor [9]. The sequence of layers is shown in Fig.…”

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Phonon sidebands of intersubband absorption in AlGaN/GaN high-electron-mobility transistors

Wang

Reimann

Woerner

et al. 2006

Physica E: Low-dimensional Systems and Nanostructures

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Femtosecond two-color pump-probe experiments in the mid-infrared are performed on intersubband transitions in a GaN=Al 0:8 Ga 0:2 N heterostructure. In these experiments, we observe around zero time delay distinct phonon sidebands, which disappear because of spectral diffusion with a time constant of 80 fs. The signal itself decays with a time constant of 380 fs. The independent boson model agrees very well with all observed results.

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“…In order to reach longer wavelength and consequently to reach THz (30-200µm), we need to change the aluminum content of the barrier. 6 Indeed, decreasing the aluminum content leads to decrease the well/barrier band offset. For example, with a 33% aluminum content the band offset is E offset = 0.58eV.…”

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Development of III-Nitride Based THz Inter-Subband Lasers

Razeghi¹

2009

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. III-Nitrides, due to their large conduction band offset and fast transition speeds, are promising constituents for intersubband (ISB) devices. In addition, III-Nitrides are characterized by a very large phonon energy (90 meV). This makes them ideally suited to the realization of near room temperature operating THz lasers. The objective of this program has been to demonstrate the potential for using III-Nitrides to realize a room temperature operating terahertz intersubband laser. In addition, III-Nitrides are characterized by a very large phonon energy (90 meV). This makes them ideally suited to the realization of near room temperature operating THz lasers. The objective of this program has been to demonstrate the potential for using III-Nitrides to realize a room temperature operating terahertz intersubband laser.As part of this contract, a comprehensive model of intersubband transitions was developed that takes into account the important effects of strain on bandstructure and piezo-as well as spontaneous-electric fields. Interband photoluminescence and intersubband absorption measurements were performed to help develop the modeling. We demonstrated the shortest MOCVD-grown III-Nitride intersubband absorption wavelength of 1.5 ?m as well as the longest intersubband wavelengths of 5.3 ?m, by any growth technique. In addition to investigating the optical properties we fabricated and tested both resonant tunneling diodes and quantum well infrared photodetectors in order to investigate quantum transport in III-Nitrides. Based on the refined III-Nitride intersubband models designs were also developed for room temperature terahertz emission via optical pumping. Electrical injection designs were also proposed for both polar and non-polar growth orientations. "Material and design engineering of (Al)GaN for high-performance avalanche photodiodes and intersubband applications," SPIE

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Midinfrared intersubband absorption on AlGaN/GaN-based high-electron-mobility transistors

Cited by 31 publications

References 16 publications

Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

Optical Phonon Sidebands of Electronic Intersubband Absorption in Strongly Polar Semiconductor Heterostructures

Phonon sidebands of intersubband absorption in AlGaN/GaN high-electron-mobility transistors

Development of III-Nitride Based THz Inter-Subband Lasers

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