New Prospect for Optoelectronics

2014

NSTOA

Self Cite

The role and application of bound excitons in nanoscience and technology are discussed in this chapter. Bound excitons are well studied in semiconductors, especially in gallium phosphide doped by nitrogen (GaP:N). Doping of GaP with N leads to isoelectronic substitution of the host P atoms by N in its crystal lattice and to creation of the electron trap with a giant capture cross-section. Therefore, any non-equilibrium electron in the vicinity of the trap will be captured by N atom, attracting a nonequilibrium hole by Coulomb interaction and creating the bound exciton -short-lived nanoparticle with the dimension of the order of 10nm (it is the Bohr diameter of bound exciton in GaP:N). Note, that none of nanotechnology methods are used in creation or selection of dimensions of these nanoparticles -only natural forces of electron-hole interaction and electron capture by the traps are necessary for creation of these nanoparticles. As the result we get something like neutral short-lived atom analoguea particle consisting of heavy negatively charged nucleus (N atom with captured electron) and hole. So called "zero vibrations" do not destroy possible solid phase of bound excitons having these heavy nuclei that gives an opportunity to reach their crystal state -short-lived excitonic crystal.Thus using bound excitons as short-lived analogues of atoms and sticking to some specific rules, including the necessity to build in the GaP:N single crystal the excitonic super lattice with the identity period equal to the bound exciton Bohr dimension, we get a unique opportunity to create a new solid state media -consisting from short-lived nanoparticles excitonic crystal, obviously, with very useful and interesting properties for application in optoelectronics, nanoscience and technology. The following will discuss methods of preparation and possible application of GaP excitonic crystals and nanocrystals in optoelectronics. Preparation and Properties of GaP with Ordered Position of N ImpuritiesCrystals that are grown under conventional laboratory conditions naturally contain a varied assortment of defects such as displaced host and impurity atoms, vacancies, dislocations, and impurity clusters. These defects result from relatively rapid growth conditions and inevitably lead to the deterioration of optical and mechanical properties of the crystal. For instance, defects in freshly-prepared GaP:N single crystals completely suppress their luminescence at room temperature, which is very bright in the same, but aged perfect crystal.With the lapse of time driving forces such as impurity diffusion, strain relaxation, and thermodynamic minimization of the free energy associated with properly directed chemical bonds can result in an ordered distribution of impurity and host atoms. Evaluation of the characteristic time of such reordering, based on the known Ising model, suggests that the time for the substitution reaction associated with N diffusion along P sites in GaP:N is about 15 years at room temperature [1]. Accordingly, observations ...

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Section: Preparation and Properties Of Gap With Ordered Position Of Nmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Excitonic Crystal and Nanotechnology

2014

NSTOA

Self Cite

Excitonic Crystal and Nanotechnology

2014

NSTOA

Self Cite

The role and application of bound excitons in nanoscience and technology are discussed in this chapter. Bound excitons are well studied in semiconductors, especially in gallium phosphide doped by nitrogen (GaP:N). Doping of GaP with N leads to isoelectronic substitution of the host P atoms by N in its crystal lattice and to creation of the electron trap with a giant capture cross-section. Therefore, any non-equilibrium electron in the vicinity of the trap will be captured by N atom, attracting a nonequilibrium hole by Coulomb interaction and creating the bound exciton -short-lived nanoparticle with the dimension of the order of 10nm (it is the Bohr diameter of bound exciton in GaP:N). Note, that none of nanotechnology methods are used in creation or selection of dimensions of these nanoparticles -only natural forces of electron-hole interaction and electron capture by the traps are necessary for creation of these nanoparticles. As the result we get something like neutral short-lived atom analoguea particle consisting of heavy negatively charged nucleus (N atom with captured electron) and hole. So called "zero vibrations" do not destroy possible solid phase of bound excitons having these heavy nuclei that gives an opportunity to reach their crystal state -short-lived excitonic crystal.Thus using bound excitons as short-lived analogues of atoms and sticking to some specific rules, including the necessity to build in the GaP:N single crystal the excitonic super lattice with the identity period equal to the bound exciton Bohr dimension, we get a unique opportunity to create a new solid state media -consisting from short-lived nanoparticles excitonic crystal, obviously, with very useful and interesting properties for application in optoelectronics, nanoscience and technology. The following will discuss methods of preparation and possible application of GaP excitonic crystals and nanocrystals in optoelectronics.Crystals that are grown under conventional laboratory conditions naturally contain a varied assortment of defects such as displaced host and impurity atoms, vacancies, dislocations, and impurity clusters. These defects result from relatively rapid growth conditions and inevitably lead to the deterioration of optical and mechanical properties of the crystal. For instance, defects in freshly-prepared GaP:N single crystals completely suppress their luminescence at room temperature, which is very bright in the same, but aged perfect crystal.With the lapse of time driving forces such as impurity diffusion, strain relaxation, and thermodynamic minimization of the free energy associated with properly directed chemical bonds can result in an ordered distribution of impurity and host atoms. Evaluation of the characteristic time of such reordering, based on the known Ising model, suggests that the time for the substitution reaction associated with N diffusion along P sites in GaP:N is about 15 years at room temperature [1]. Accordingly, observations of the luminescence from GaP:N crystals made at 10-15 year intervals unde...

Excitonic Crystal, Nanotechnology and New Prospect for Optoelectronics

2015

TOOPTSJ

The review demonstrates the results of development of growth technology for perfect and free of contamination gallium phosphide (GaP) crystals and investigation of influence of crystallization conditions on quality and properties of the crystals. The long-term ordered and therefore close to ideal crystals repeat behavior of the best nanoparticles with pronounced quantum confinement effect. These perfect crystals are useful for application in top-quality optoelectronic devices as well as they are a new object for development of fundamentals of solid state physics.Since the time of original preparation by the author in the 1960s of gallium phosphide crystals doped by nitrogen (GaP:N), followed by the introduction of the excitonic crystal concept in the 1970s, the best methods of bulk, film and nanoparticle crystal growth were elaborated. The results of semi centennial evolution of GaP:N properties are compiled in the paper. Novel and useful properties of perfect GaP including its stimulated emission, very bright and broadband luminescence at room temperature were observed. These results provide a new approach to selection and preparation of perfect materials for optoelectronics and a unique opportunity to realize a new form of solid-state host -the excitonic crystal as high intensity light source with expected low threshold for generation of non-linear optical effects.Using the example of GaP, here is proposed the cheap, resource-saving and impactful way for development of optoelectronics with the help of a special transformation of an ordinary semiconductor into the base material for various device structures.