IR Lasers on Low-Dimensional Semiconductor Structures
Development of Physical Principles of New Type Far and Mid IR Lasers Based on Low Dimensional Semiconductor Structures
Tech Area / Field
- PHY-OPL/Optics and Lasers/Physics
- PHY-SSP/Solid State Physics/Physics
8 Project completed
Senior Project Manager
Bunyatov K S
Institute of Physics of Microstructures, Russia, N. Novgorod reg., N. Novgorod
- State University of Nizhny Novgorod, Russia, N. Novgorod reg., N. Novgorod\nVNIIEF, Russia, N. Novgorod reg., Sarov\nSt Petersburg State Polytechnical University, Russia, St Petersburg
- University of Tokyo / Department of Basic Science, Japan, Tokyo\nUniversity of Sheffield, UK, Shiffield\nLos-Alamos National Laboratory, USA, NM, Los-Alamos\nLos Alamos National Laboratory, USA, NM, Los-Alamos
Project summaryThe proposal is aimed at the development of physical principles of new type mid and far IR lasers based on quantum semiconductor structures. The laser structures of a simple energy design will be grown using an ordinary technology. The lasers will be distinguished by improved functionality and a possibility to operate in a broad spectral range. These devises could be widely applied in the laboratory spectroscopy as well as in the communication technique, environment monitoring, metrology, biology, medicine, radioastronomy etc. To the moment at the long wavelength end of IR range there exist only hot hole bulk Ge lasers operating at liquid helium temperatures in pulsed mode. The effectiveness of the traditional mid IR lasers emitting at interband transitions is limited by nonradiational processes and Auger recombination. In recent years the lasers operating at interlevel transitions in quantum well heterostructures (l=2-17 mm) have been developed. In quantum cascade lasers the possibility of promotion to the far IR range is restricted by the existence of highly doped contact regions just near the waveguide thus resulting in large losses. In so called fountain laser the excitation is provided by a powerful CO2-laser that restrict significantly the generated wavelength tuning and the possible applications of the devise.
In the framework of the project new mechanisms of generation of radiation at intraband transitions of charge carriers in quantum well (QW) and quantum dot (QD) structures based on A3B5 semiconductors and Si/SiGe heterostructures:
– population inversion in QW heterostructures in high electric fields under real space transfer and intervalley transfer of hot carriers;
– intracenter population inversion between resonant and localized states of shallow impurities in QW and QD heterostructures;
– intraband population inversion in QW and QD heterostructures under stimulated interband emission of near IR radiation (two-color laser).
The key information on the energy spectra of the real structures that is important for the realization of the above tasks will be obtained by the investigations of intraband absorption in QW and QD heterostructures in strong (up to several megagauss) magnetic fields. At the final stage of the project new types of the lasers for mid and far IR range will be designed. Prototypes of the devices will be manufactured. Physical processes in the devices will be investigated and the main characteristics of the lasers will be determined.
All scientific teams participating in the project are skilled in the growth and the investigation of semiconductor QW and QD structures, their experience being complementary. IPM and StPSTU participated in a design and construction of hot hole far IR laser in Ge. They have long standing experience of collaboration including that in the investigation of hot carriers in low-dimensional semiconductor structures. The universal mechanism for population inversion in QW structures in high lateral electric field under real space and intervalley transfer has been proposed by IPM team. This group also investigated resonant states of shallow impurities. StPSTU scientists suggested two-color (near and mid IR) laser. Theoretical estimates and the first results of numerical simulation allow to suppose a gain of 20-100 cm-1 in the wavelength range 10-100 mm. NNSU group completed a cycle of theoretical studies on magnetooptics of two-dimensional (2D) superlattices consisted of QDs. Novel computational technique for the investigation of quantum states of Bloch electron in a magnetic field has been developed. Cyclotron resonance (CR) spectra of 2D holes in Ge/GeSi QW heterostructures were investigated for the first time by IPM team. In RFNC – VNIIEF the unique generator of ultrahigh magnetic fields up to 1,000 T has been constructed and the techniques of CR and magnetooptical absorption study in such strong magnetic fields has been elaborated. A cycle of low-dimensional semiconductor structures investigations in megagauss magnetic fields has been performed. IPM team is skilled in molecular beam epitaxy (MBE) growth of Si structures with self-organized Ge QDs. NNSU team acquired experience in chemical vapor deposition (CVD) of A3B5 QW and QD heterostructures as well as in the construction of interband injection IR lasers. For many years it has close collaboration with IPM group.
In the framework of the project the laboratory techniques of CVD and MBE growth of QW and QD heterostructures for mid and far IR lasers will be developed. The parameters of energy spectra of free carriers and impurity states necessary for the laser design based on low-dimensional A3B5 and Si/SiGe structures will be determined. The mechanisms of the population inversion of hot carriers in high lateral electric fields under real space and intervalley transfer as well as at a capture of charge carriers at resonant impurity states will be elaborated. The population inversion diagnostics techniques will be developed and the conditions for its origin will be revealed; the gain values will be determined. Optical phenomena in mid IR range in QW and QD structures intended for two-color laser under optical band-gap and current excitation of non equilibrium carriers will be investigated. Based on the results obtained optimal energy band structures and QW and QD semiconductor heterostructure laser design for far and mid IR ranges will be chosen. Prototypes of the devises will be constructed and their characteristics will be measured.
Most of the project participants from Russia were involved in the weapons development. The participation in the project will promote their reorientation to the civil activity, development of basis and applied investigations of low-dimensional quantum semiconductor structures for peaceful purposes. R&D results obtained in the framework of the project will bring to construction of competitive devices, enable the vent of Russian leading science and technology centers to the market of high civil technologies. Therefore the execution of project tasks will contribute to the realization of ISTC aims and tasks.
Corresponding to the project objectives the proposed activity is shared into 9 closely related main tasks. The first one is connected with the growth and characterization of semiconductor QW and QD heterostructures for the scientific research and device prototype construction. Tasks 2-7 will be solved in parallel. They are aimed at the development of mechanisms of creation of population inversion and amplification in mid and far IR range as well as at the detailed investigation of energy band diagrams of the heterostructures chosen for the lasers construction. The result of the activity in the framework of the project should be the design of mid and far IR lasers and construction of the devises prototypes (task 8).
Administrative management of the project stipulates continual consultations between Russian participants and carrying out joint investigations, intensive exchange by information with foreign collaborators, organizing joint seminars/workshops. The main scientific results obtained (tasks 2-8) are to be published in international an leading Russian scientific journals and reported at Russian and international scientific conferences.
Participation of the foreign collaborators in the project will make the work more attractive and will further promote its successful fulfillment. IPM team has performed joint study with Prof. S. Komiyama group (The University of Tokyo) on sensitive tunable far IR detectors operating at cyclotron resonance of 2D electrons under quantum Hall effect conditions. A cooperative investigation of resonant states of shallow impurities and generation of far IR radiation at optical transitions between resonant and localized shallow impurity states in QW heterostructures is planed. Both the Japanese and IPM groups are experienced in the investigation of far IR stimulated emission in bulk p-Ge. Prof. J. Cockborn group (Sheffield University, UK) is experienced in the investigations of intersubband population inversion in QW heterostructures, spontaneous and stimulated mid IR emission from GaAs/AlGaAs quantum cascade lasers. It has already established scientific cooperation with StPSTU and IPM teams in the frameworks of INTAS-RFBR 95-0615 and INTAS 99-1242 projects.
QW and QD heterostructures will be grown at NNSU using atmospheric pressure CVD machine (A3B5) and at IPM using MBE machines "Balzers" UMS 500P и "Katun" (Si/Ge). There is necessary equipment for photolithography, contact deposition, structure studies of the sample, Hall effect measurement in a broad temperature range 4.2-300 K and photoluminescence study.
Investigations of electron transport and spontaneous far and mid IR emission in the heterostructures in high lateral electric fields will be carried out at IPM using pulsed technique. Spectral study of the spontaneous emission will be made using tunable by the magnetic field detectors. Diagnostics of hot carrier distributions will be done on the base of band gap luminescence and absorption spectra measured at Russian spectroscopy complex KSVU-23. Experimental study of localized and resonant shallow impurity states will be carried out at IPM using BOMEM” DA3-36 Fourier-transform spectrometer. Spectra of recombination radiation at impact ionization of shallow impurities in lateral electric fields will be studied by means of tunable by the magnetic field cryogenic detectors. Experimental study of magnetoabsorption (at wavelength 1.15 and 3.39 mm using He-Ne laser) and cyclotron resonance (at wavelength 10 mm using СО2 laser) in QW and QD heterostructures at megagauss magnetic fields will be carried out at VNIIEF using ultrahigh magnetic field generator. Optical absorption in mid IR range in nanostructures intended for two-color laser will be investigated at StPSTU using multiple-pass technique. Spontaneous mid IR emission will be studied at intensive pulses optical pumping exceeding band gap generation threshold. Both the spontaneous mid IR and the stimulated near IR radiation will be investigated at the same time.
Apart from development of simple physical models for the population inversion description, numerical simulation of electron transport and distribution functions my Monte-Carlo technique will be carried out. Besides of personal computers (Celeron, Pentium II), being at the moment at IPM and NNSU research groups disposal, a new workstation based on Pentium III processor (1 GHz, 256 MB) purchased at the expense of the project budget will be utilized for these purposes. At the theoretical calculations of gain amplitudes and spectra in mid and far IR ranges the results of experimental and theoretical studies obtained at the solution of tasks 2-7 will be used. At the design of laser resonator and waveguide systems the emphasis will be done electrodynamical calculations of wave fields for different ways of space restriction of radiation and waveguide realization in the structures (epitaxy growth of layers with less dielectric permittivity, deposition of amorphous Ge layer, substrate back side profiling).
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