Intersubband spectroscopy of doped and undoped GaN/AlN quantum wells grown by molecular-beam epitaxy

Helman, A.; Tchernycheva, Maria; Lusson, A.; Warde, E.; Julien, F. H.; Moumanis, Kh.; Fishman, G.; Monroy, E.; Daudin, B.; Dang, Daniel Le Si; Bellet‐Amalric, E.; Jalabert, D.

doi:10.1063/1.1635985

Cited by 86 publications

(61 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…7,8 Unfortunately, the heavy effective masses of 0.2 m e for GaN and 0.32 m e for AlN impose the epitaxial growth of layer thicknesses in the 15-30 Å range, which, despite substantial progress in molecular beam epitaxy, is still quite a challenging task. 9 Nevertheless, intersubband absorption down to 1.06 m has been shown in heavily doped, ultrathin GaN quantum wells which were separated by barriers of either AlGaN, pure AlN, or AlN/GaN superlattices. 10,11 In the majority of these experiments, the observed effects were purely optical and, except for one report, no vertical current transport could be demonstrated.…”

mentioning

confidence: 99%

Tunneling effects and intersubband absorption in AlN/GaN superlattices

Baumann

Giorgetta

Hofstetter

et al. 2005

Applied Physics Letters

View full text Add to dashboard Cite

We report on intersubband absorption and photovoltage measurements on regular GaN/AlN-based superlattice structures. For barrier thicknesses larger than about 25 Å, the optical intersubband absorption peaks at a considerably smaller energy than the photovoltage spectrum. A simple model taking into account the oscillator strength of the involved transitions and the corresponding tunneling probabilities agrees with the experimental findings. According to this model, the observed photovoltage is the macroscopic manifestation that the two-dimensional electron gas at the top of the superlattice changes its carrier density by a vertical transport of electrons.Thanks to their large band gap energies, the semiconductor materials GaN and AlN have attracted a lot of attention for the fabrication of long-lived visible lasers and lightemitting diodes. 1-3 More recently, the huge conduction band discontinuity of nearly 2 eV between these two semiconductors has resulted in some device proposals based on intersubband transitions. [4][5][6] Particularly interesting in this context are photodetectors, modulators, or lasers in the technologically interesting 1.55 m wavelength range. Such devices could profit from short intersubband lifetimes, which might eventually result in high operating frequencies. 7,8 Unfortunately, the heavy effective masses of 0.2 m e for GaN and 0.32 m e for AlN impose the epitaxial growth of layer thicknesses in the 15-30 Å range, which, despite substantial progress in molecular beam epitaxy, is still quite a challenging task. 9

show abstract

mentioning

confidence: 99%

Tunneling effects and intersubband absorption in AlN/GaN superlattices

Baumann

Giorgetta

Hofstetter

et al. 2005

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…There are several studies of intersubband absorption in AlN/GaN heterostructures. [1][2][3][4][5][6] These typically show a peak at 500 to 900 meV with full width half maximum (FWHM) in the range of 60 to 200 meV. An intersubband device should operate at and above 300 K, often with the condition of a negligible change in transition energy.…”

mentioning

confidence: 99%

Temperature stability of intersubband transitions in AlN/GaN quantum wells

Berland

Stattin

Farivar

et al. 2010

Applied Physics Letters

View full text Add to dashboard Cite

Temperature dependence of intersubband transitions in AlN/GaN multiple quantum wells grown with molecular beam epitaxy is investigated both by absorption studies at different temperatures and modeling of conduction-band electrons. For the absorption study, the sample is heated in increments up to 400 • C. The self-consistent Schrödinger-Poisson modeling includes temperature effects of the band-gap and the influence of thermal expansion on the piezoelectric field. We find that the intersubband absorption energy decreases only by ∼ 6 meV at 400 • C relative to its room temperature value.Intersubband transitions in nitride-based semiconductor heterostructures hold great promise for optoelectronic devices. The high band-offset between gallium nitride (GaN) and aluminum nitride (AlN) enables intersubband transitions in the near-infrared regime (λ = 1-4 µm). Thus, intersubband devices such as modulators, detectors, and quantum cascade lasers (QCLs) have the potential to operate at wavelengths useful for fiberoptic communication. QCLs also have the potential to be used when measuring characteristic absorption of small molecules. There are several studies of intersubband absorption in AlN/GaN heterostructures.[1-6] These typically show a peak at 500 to 900 meV with full width half maximum (FWHM) in the range of 60 to 200 meV. An intersubband device should operate at and above 300 K, often with the condition of a negligible change in transition energy. Temperature dependence of the transition energy, up to room temperature, has been reported for intersubband absorption in InAs/AlSb multiple quantum well (MQW) structures [7] and for interband photoluminescence in nitride-based AlN/GaN MQW structures.[8] The huge piezoelectric fields introduce an additional temperature-dependent effect in the nitride MQW structures, because the different thermal expansions of AlN and GaN induce a temperature dependent strain in the structures.In this letter, we demonstrate that the peak position of intersubband transitions red shifts only ∼ 6 meV as the temperature of the sample is increased from 25 • to 400 • C. This aspect of thermal robustness could be vital for the operation of nitride-based QCLs since their ultrafast LO-scattering rates and high intersubband energy would cause them to heat significantly. The temperature effects are studied for MQW structures both experimentally by measuring the absorption at different temperatures, and theoretically by a self-consistent solution to the Schrödinger-Poisson equations for the conductionband electrons. The nitride-semiconductor heterostructures are characterized by huge internal electric fields, which arise from the exceptionally large spontaneous and piezoelectric fields. A proper account of these fields are crucial for an accurate description and characterization of the quantum well states, and they require that the complete structure is considered in the design of heterostructures.The set of MQW structures (A -C) are grown in a Varian Gen II modular molecular beam epitaxy (MBE) system....

show abstract

“…Furthermore, in situ monitorization of the surface morphology by reflection high energy electron diffraction (RHEED) makes possible to control the growth at the atomic layer scale. Room temperature ISB absorption at λ ≈ 1.3−1.55 has been demonstrated in both QW [4][5][6][7][8] and QD superlattices [9][10][11], and several prototypes of ISB detectors [12][13][14][15] and electro-optical modulators [16] have recently been reported. These developments are possible thanks to improved deposition techniques for Al(Ga)N/GaN layers and superlattices [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

III-Nitride Nanostructures for Infrared Optoelectronics

et al. 2006

Self Cite

View full text Add to dashboard Cite

Thanks to their large conduction band offset (∼ 1.8 eV for the GaN/AlN system) and subpicosecond intersubband scattering rates, III-nitride heterostructures in the form of quantum wells or quantum dots are excellent candidates for high-speed unipolar devices operating at optical-fiber telecommunication wavelengths, and relying on the quantum confinement of electrons. In this work, we present the plasma-assisted molecular-beam epitaxial growth of quantum well infrared photodetector structures. The growth of Si-doped GaN/AlN multiple quantum well structures is optimized by controlling substrate temperature, metal excess and growth interruptions. Structural characterization confirms a reduction of the interface roughness to the monolayer scale. P -polarized intersubband absorption peaks covering the 1.33−1.91 µm wavelength range are measured on samples with quantum well thickness varying from 1 to 2.5 nm. Complete intersubband photodetectors have been grown on conductive AlGaN claddings, the Al mole fraction of the cladding matching the average Al content of the active region. Photovoltage measurements reveal a narrow (∼ 90 meV) detection peak at 1.39 µm at room temperature.

show abstract

Intersubband spectroscopy of doped and undoped GaN/AlN quantum wells grown by molecular-beam epitaxy

Abstract: Structural and vibrational properties of molecular beam epitaxy grown cubic (Al, Ga)N/GaN heterostructures

Cited by 86 publications

References 14 publications

Tunneling effects and intersubband absorption in AlN/GaN superlattices

Tunneling effects and intersubband absorption in AlN/GaN superlattices

Temperature stability of intersubband transitions in AlN/GaN quantum wells

III-Nitride Nanostructures for Infrared Optoelectronics

Contact Info

Product

Resources

About