Light emitting devices with a zinc oxide thin film structure
OwnerBrian Rioux, Jean-Paul Noelinventors
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Abstract
The present invention relates to a sol-gel deposition/heat treatment process, which consistently produces polycrystalline direct bandgap semiconductor, e.g. ZnO, thin films exhibiting a photo luminescent (PL) spectrum at room temperature that is dominated by a single peak, e.g. in the ultraviolet part of the spectrum, in which the PL intensity of the bandgap emission is more than approximately 40 times greater than any deep-level defect emission peak or band. The present invention incorporates such direct bandgap semiconductor, e.g. ZnO, polycrystalline thin films produced by the method of the present invention into electro-luminescent devices that exhibit similarly high ratios of bandgap/deep-level defect emission intensity.
Claims19
A light emitting structure comprising:
- an active layer structure including:
- a direct bandgap semiconductor material with a free-exciton binding energy greater than 25 meV, enabling free-excitons, each comprising an electron and a hole, to exist at room temperature, and
- a dopant for populating the direct bandgap semiconductor material with free-exciton binding centers in a concentration greater than or equal to a native defect concentration in the direct bandgap semiconductor material, wherein the binding energy of either the electron or the hole of each of the free excitons to the dopant binding center is also greater than 25 meV;
- and
- an excitation source or mechanism for generating electron-hole pairs in the direct bandgap semiconductor material to produce substantial populations of excitons;
- whereby the binding centers provided by the dopant increase probability of free-exciton to bound-exciton formation in the direct bandgap semiconductor material for generating efficient near-bandgap-emission of light.
A method of forming a direct bandgap semiconductor material polycrystalline film comprising the steps of:
- a) providing a direct bandgap semiconductor material precursor;
- b) providing a dopant precursor for populating crystallites within the polycrystalline film with optically active free-exciton binding centers in concentrations above a native defect concentration;
- c) placing the direct bandgap semiconductor material precursor in a solvent with a stabilizing compound forming a mixture;
- d) dissolving the dopant precursor in the mixture;
- e) dispensing the mixture onto a wafer forming the direct bandgap semiconductor material film with dopant therein;
- and
- f) baking the film to fully crystallize the film, promote grain growth, and minimize the concentration of native intra-crystal defects, thereby substantially increasing the probability that free excitons will encounter and bind to the optically active binding centers before encountering a defect site.
Dependencies are inferred from the claim text.