Laser Epitaxy for Semiconductor Technology
New Technology of Preparation of High Stoichiometric Semiconducting Structures and Solid Solutions by the Method of Laser Pulse Epitaxy
Tech Area / Field
- MAN-MAT/Engineering Materials/Manufacturing Technology
- MAT-ELE/Organic and Electronics Materials/Materials
8 Project completed
Senior Project Manager
Komarkov D A
Institute of Radiophysics and Electronics, Armenia, Ashtarak-2
- University of Maryland / Department of Materials and Nuclear Engineering, USA, MD, College Park\nUniversity of Virginia / School of Engineering and Applied Science, USA, VA, Charlottesville\nDepartment of the Navy / Naval Research Laboratory, USA, DC, Washington\nInstitute of Electronic Structure & Laser, Greece, Heraklione
Project summaryAt present semimetals and narrow band gap semiconductors form a separate group of materials from the point of view of peculiarities of the technological processes for obtaining them, the specificity of their physical properties and research techniques; applications of the materials of this group are also rather specific. The high sensitivity of their electronic systems to external influences, in particular, ample opportunities of transformation of the energy spectrum of charge carriers, allows application of these materials in various solid state devices. Thus, the development of apparatus for detection and generation of infrared (IR) radiation based on narrow gap semiconductors has allowed essentially to master the IR range of electromagnetic radiation. Note that semimetals and narrow bandgap semiconductors, due to the high characteristic lengths (de-Broigle wavelengths, free electron path lengths, etc.), are also interesting systems for the study of dimensionally-quantized effects. However, despite recent achievements, many aspects of the physics which occur in these devices are still not well understood.
The modern process of growing semiconducting A4B6 compositions is such, that the crystallization occurs with considerable deviations from stoichiometry, which results in an occurrence of high concentrations of charge carriers. This restricts the possibility of promoting in long wavelength region of detection and generation of electromagnetic radiation, and also the realization of high field experiments, where extra bands should reveal themselves. The known method of reduction of free carrier concentration by the self-compensating has allowed to lower concentration of free carriers in PbTe only to magnitude 1015 cm-3, whereas the natural concentration of carriers for PbTe at T=78 K has a magnitude ≤ 1011 cm-3 (p=1.51016 cm-3 for T=300 K). Therefore, the development of a new technological processes for obtaining semiconducting materials with a composition A4B6, in particular, Te compounds with tin and lead, with governed stoichiometry, ensuring the possibility of obtaining much lower concentrations of free carriers, is a rather actual problem.
The Bi1-xSbx alloys, which form a continuous series of solid solutions with monotonic dependence of lattice parameters and essential dependence of the energy spectrum of charge carriers on a composition of a solution, are also characteristic representatives of narrow gap semiconductors.
In the concentrations range 0.085<x<0.22 solutions of Bi1-xSbx are narrow gap semiconductors with high thermoelectric characteristics, that pre-determines wide possibilities of using these materials for constructing high sensitivity thermoelectric and thermomagnetic energy transformers, detectors and generators of radiation in remote IR range.
The charge carriers in Bi1-xSbx have a small effective mass (<10-2 m0, m0 is the mass of the electron) and high mobility, that makes the solutions Bi1-xSbx a convenient medium for creating Bi-Sb-Bi-Sb- … superlattices.
The prospect of the further development of methods for preparation and application of Bi1-xSbx alloys is connected with the possibility of developing film materials, which can be conjugated with other systems on corresponding substrates.
In this Project it is proposed to carry out complex investigations with a purpose of:
– development of a new technology of using the method of laser pulse epitaxy (LPE) for production (from elementary Pb, Sn, Te sources) of semiconducting hyperfine films of Te compounds of tin and lead and multilayer structures based on them on policore, mica and silicon substrates with governed stoichiometry with the corresponding concentration of free n, p current carriers in an interval 1012 cm-3 (at T=78 K)≤ n, p≤1018 cm-3;
– development of a new technology using the LPE method for production of solid solutions of Bi1-xSbx, varizone structures Bi1-xSbx with a value x varying in a direction of growth of a film, and also multilayer structures Bi-Sb-Bi-Sb- … on mica and bismuth substrates.
The aims of the project are:
– development of a physical foundations of laser deposition of high stoichiometric monocrystal layers PbTe, Pb1-xSnxTe on policor (polycrystalline corundum), mica and silicon substrates;
– realization of complex measurements of structural, photoelectric and optical parameters of obtained samples and establishment of connection of these parameters with technological parameters (temperature of a substrate, target – substrate distance, intensity of laser radiation, level of vacuum);
– creation of Si-PbTe, Si-Pb1-xSnxTe heterojunctions (HJ) with various thickness of PbTe, Pb1-xSnxTe layers and multilayer structures based on them;
– development of a new technology of using the method of LPE for production of solid solutions Bi1-xSbx of different compositions and varizone structures Bi1-xSbx using elementary sources of Bi and Sb;
– development of a new multilayer Bi-Sb-Bi-Sb-… structures using elementary sources of Bi and Sb under the condition of their immiscibility.
– decrease of crystalline growth temperature of rigid solutions of Te compounds with tin and lead;
– production of high stoichiometric films of PbTe, Pb1-xSnxTe with given concentration of free carriers n, p≥1012 cm-3 on policor, mica and silicon substrates;
– realization of crystalline growth of the PbTe, Pb1-xSnxTe films on Si substrates under a condition excluding the interdiffusion;
– production of PbTe-Si, Pb1-xSnxTe-Si HJ with sharp transition boundary;
– development of multilayer pSi-PbTe- Pb1-xSnxTe-PbTe- - nSi structures with dimensionally quantized layers;
– realization of crystalline growth of Bi-Sb at low temperatures;
– development of thin-film Bi1-xSbx solid solutions displaying the effects of dimensional quantization;
– production of varyzone Bi1-xSbx structures;
– production of multilayer Bi-Sb- Bi-Sb-… structures with sharp transition boundaries.
These results will ensure considerable improving of parameters (sensitivity, fast-action, etc.) of optoelectronic devices using a proper photoeffect in IR and remote IR range of wavelengths.
The realization of the present Project will be accomplished by a team including 3 doctors of phys. math. sciences, 2 candidates of phys. math. sciences, 8 physisicsts and engineers, and also qualified technicians having experience of working in the field of the investigations within the Project. The leading participants of the Project were involved during many years in development of new technological methods for production of superpure high stoichiometric semiconducting films. The results of explorations carried out by them are published in materials of international conferences and scientific journals (Inter. Jour. of Infrared and Millimeter Waves, Quantovaya Elektronika (Rus), Journal of Contemporary Phisics (Armenian Academy of Sciences) etc.).
The proposed Project corresponds to the status ISTC and is caused by necessity of making of alternatives for the scientist and engineers, previously engaged in defense programs.