Direct observation of spin-orbit splitting and phonon-assisted optical transitions in the valence band by internal photoemission spectroscopy

Lao, Yan-Feng; Perera, A. G. U.; Li, L. H.; Khanna, Suraj P.; Linfield, E. H.; Liu, H. C.

doi:10.1103/physrevb.88.201302

Cited by 6 publications

(3 citation statements)

References 48 publications

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“…26,27 It was shown that the carrier-phonon coupling plays an important role in the intervalence-band transitions. 28 Photoexcited holes in the light-hole band or spin-orbit split-off band initially relax, mainly through the emission of optical phonons, typically within a sub-picosecond timescale. The subsequent relaxation proceeds through the dominant hole-hole scattering mechanism, which causes a redistribution of energies among the hot and cold holes.…”

Section: Hot-cold Carrier Interactionsmentioning

confidence: 99%

Tunable hot-carrier photodetection beyond the bandgap spectral limit

Lao

Perera

et al. 2014

Nature Photon

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The spectral response of common optoelectronic photodetectors is restricted by a cutoff wavelength limit (λ c) that is related to the activation energy (or band-gap) of the semiconductor structure (or material) (∆) through the relationship: λ c = hc/∆. This spectral rule dominates device design and intrinsically limits the long wavelength response of a semiconductor photodetector. Here, we report a new, long wavelength photodetection principle based on a hot-cold hole energy transfer mechanism that overcomes this spectral limit. Hot carriers injected into a semiconductor structure interact with cold carriers and excite them to higher energy states. This enables a very long-wavelength infrared response. In our experiments, we observe a response up to 55 µm, which is tunable by varying the degree of hot-hole injection, for a GaAs/AlGaAs sample with ∆ = 0.32 eV (equivalent to 3.9 µm in wavelength).

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Section: Hot-cold Carrier Interactionsmentioning

confidence: 99%

Tunable hot-carrier photodetection beyond the bandgap spectral limit

Lao

Perera

et al. 2014

Nature Photon

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“…2A , where it can be seen that the peak responsivity is 7.3 A/W, which is about five orders of magnitude higher than that of the OPHED; for the responsivity calibration method, see the Supplementary Materials. The near-IR (NIR; 80 to 300 THz) photoresponse mechanism is caused by the SO band absorption (SOA) and consists of three main steps: (i) photoabsorption that excites the holes from the highly doped emitters (i.e., injector and absorber), where a direct transition occurs from light or heavy hole band to the SO band; (ii) scattering-assisted escape of the photoexcited carriers; and (iii) collection of the escaped carriers ( 35 , 36 ). The response mechanism of the mid-IR (MIR) and far-IR (FIR) photons (16 to 80 THz) is primarily caused by the free carrier absorption (FCA)–based internal photoemission.…”

Section: Resultsmentioning

confidence: 99%

“…4C , under the zero bias, the IR photons stochastically changed the momentum and energy of the holes in both the injector and the absorber. The occurred absorption includes the FCA and SOA ( 35 , 36 ). Then, the asymmetry of the repeated unit of the barrier potential biased the holes’ motion to the left due to the asymmetric relaxation ( 25 , 26 ).…”

Section: Resultsmentioning

confidence: 99%

Broadband and photovoltaic THz/IR response in the GaAs-based ratchet photodetector

Bai

Chu

et al. 2022

Sci. Adv.

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High-performance broadband infrared (IR)/terahertz (THz) detection is crucial in many optoelectronic applications. However, the spectral response range of semiconductor-based photodetectors is limited by the bandgaps. This paper proposes a ratchet structure based on the GaAs/Al x Ga 1− x As heterojunction, where the quasi-stationary hot hole distribution and intravalence band absorption from light or heavy hole states to the split-off band overcome the bandgap limit, ensuring an ultrabroadband photoresponse from near-IR to THz region (4 to 300 THz). The peak responsivity of the proposed structure can reach 7.3 A/W, which is five orders of magnitude higher than that of the existing broadband photon-type detector. Because of the ratchet effect, the proposed photodetector has a bias-tunable photoresponse characteristic and can operate in the photovoltaic mode with a broad photocurrent spectrum (18 to 300 THz). This work not only demonstrates a broadband photon-type THz/IR photodetector but also provides a method to study the light-responsive ratchet.

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Optical characteristics of p-type GaAs-based semiconductors towards applications in photoemission infrared detectors

Lao

Perera

Wang

et al. 2016

Journal of Applied Physics

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Free-carrier effects in a p-type semiconductor including the intra-valence-band and inter-valence-band optical transitions are primarily responsible for its optical characteristics in infrared. Attention has been paid to the inter-valence-band transitions for the development of internal photoemission (IPE) mid-wave infrared (MWIR) photodetectors. The hole transition from the heavy-hole (HH) band to the spin-orbit split-off (SO) band has demonstrated potential applications for 3-5 lm detection without the need of cooling. However, the forbidden SO-HH transition at the C point (corresponding to a transition energy D 0 , which is the split-off gap between the HH and SO bands) creates a sharp drop around 3.6 lm in the spectral response of p-type GaAs/AlGaAs detectors. Here, we report a study on the optical characteristics of p-type GaAs-based semiconductors, including compressively strained InGaAs and GaAsSb, and a dilute magnetic semiconductor, GaMnAs. A model-independent fitting algorithm was used to derive the dielectric function from experimental reflection and transmission spectra. Results show that distinct absorption dip at D 0 is observable in p-type InGaAs and GaAsSb, while GaMnAs displays enhanced absorption without degradation around D 0 . This implies the promise of using GaMnAs to develop MWIR IPE detectors. Discussions on the optical characteristics correlating with the valence-band structure and free-hole effects are presented.

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Direct observation of spin-orbit splitting and phonon-assisted optical transitions in the valence band by internal photoemission spectroscopy

Cited by 6 publications

References 48 publications

Tunable hot-carrier photodetection beyond the bandgap spectral limit

Tunable hot-carrier photodetection beyond the bandgap spectral limit

Broadband and photovoltaic THz/IR response in the GaAs-based ratchet photodetector

Optical characteristics of p-type GaAs-based semiconductors towards applications in photoemission infrared detectors

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