Excitonic Crystal, Nanotechnology and New Prospect for Optoelectronics

Abstract

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.

New Prospect for Optoelectronics

“…Novel and useful properties of GaP including expected similarity in behavior between nanoparticles and perfect bulk crystals, as well as very bright and broadband luminescence at room temperature, are observed. These results provide a new approach to the selection and preparation of perfect materials for optoelectronics [8] and a unique opportunity to realize a new form of solid-state host-the excitonic crystal [9][10][11]. Despite the fact that the time necessary for natural long-term ordering (years) is not optimal, the collected experience and results confirm expedience of the efforts directed to the formation in GaP of the N impurity superlattice having the identity period equal to the bound exciton dimension.…”

“…Novel and useful properties of the perfect GaP were observed, including its stimulated emission, very bright and broadband luminescence at room temperature. Arguably, the best methods of bulk, film and nanoparticle crystal growth have been elaborated since [6][7][8][9][10][11].…”

“…At certain concentrations of N, the anion sub-lattice can be represented as a row of anions, where N impurities substitute P atoms with the period equal to the Bohr diameter of the bound exciton in GaP (approximately 10 nm) (Figure 5a). At some level of optical excitation, all the N sites will be filled by excitons, thereby creating an excitonic crystal (Figure 5b), which is a new phenomenon in solid-state physics and extremely interesting medium for application in optoelectronics and nonlinear optics [5][6][7][8][9][10][11].…”

“…Independently of their dimensions, they demonstrate very interesting for application properties. Therefore, tremendous commercial advantage can be achieved by using the long-term ordered, perfect GaP crystals or materials of similar behavior and properties instead of very expensive and labor-intensive technologies for diverse materials and their nanoparticles with spectral region and other parameters limited for application in the electronic industry (for details please see the papers [7][8][9][10][11]).…”

“…Main results, as they occurred and as they were understood and interpreted for more than half a century, are presented in many works. The most important ones are covered in [1][2][3][4][5][6][7][8][9][10][11]. Since pure and doped samples of Gallium Phosphide were originally prepared in the 1960s [1,2], followed by the introduction of the excitonic crystal concept in the 1970s [3], the author discovered stimulated emission with indirect optical transitions [4] and interesting non-linear optical…”