Patent Application
20140291688
1. Technical Field
This disclosure generally relates to solid state light displays, and particularly to an active matrix solid state light display comprising solid state lighting elements having stable and reliable performance.
2. Description of Related Art
A typical active matrix organic light emitting display (AMOLED) includes a plurality of organic light emitting elements functioning as light sources. However, in a manufacturing process of the active matrix organic light emitting display, the organic light emitting materials are prone to be affected by environmental factors, such as moisture, which cause the organic materials to be deteriorated. Therefore, manufacturing process of the active matrix organic light display need to be performed in a vacuum environment to avoid the deterioration of the organic materials, resulting in a complicated manufacturing process. In addition, the deterioration of the organic light emitting materials shortens the service life of the active matrix organic light displays.
What is needed, therefore, is an active matrix solid state light display which can overcome the above-described shortcoming.
Referring to
The active matrix solid state light display 10 includes a substrate 12, a plurality of solid state lighting elements 14, and a plurality of thin film transistors 16. In this figure, only one solid state lighting element 14 and one thin film transistor 16 are shown.
The substrate 12 is made of sapphire, silicon, silicon on insulator (SOI), glass, GaN, ZnO or plastic. A buffer layer 122 is formed on a top surface of the substrate 12. The buffer layer 122 is electrically insulated. The buffer layer 122 is made of at least one of LT-AlInGaN (Low Temperature AlInGaN), SiOx, SiNx, SiON, HfOx, AlOx, TaOx, or BaSrTiOx.
The solid state lighting elements 14 are formed on the buffer layer 122, and the thin film transistors 16 are formed on the substrate 12. The solid state lighting elements 14 each are a light emitting diode (LED). The solid state lighting element 14 can be selected from an oxide semiconductor, a nitride semiconductor, a phosphide semiconductor, or an arsenide semiconductor. The solid state lighting element 14 may be a compound semiconductor, including III-V semiconductors, II-VI semiconductors, or IV-IV semiconductors. In this embodiment, the solid state lighting element 14 is a P-N type light emitting diode, and includes a p-type electrode 141, a p-type semiconductor layer 142, a light emitting layer 143, an n-type semiconductor layer 144 and an n-type electrode 145.
The n-type semiconductor layer 144 is formed on the buffer layer 122. The light emitting layer 143 is formed on the n-type semiconductor layer 144. The p-type semiconductor layer 142 is formed on the light emitting layer 143. The n-type electrode 145 is formed on the n-type semiconductor layer 144. The p-type electrode 141 and the n-type electrode 145 are metal blocks or thin metal films, and are used to electrically connect with the thin film transistor 16.
A contact layer 146 and a current spreading layer 147 are located between the p-type semiconductor layer 142 and the p-type electrode 141. The current spreading layer 147 is a low contact resistant layer to help the contact layer 146 spread the current, which increases the lighting efficiency of the solid state lighting element 14.
The n-type semiconductor layer 144 can be a metal oxide semiconductor, such as ZnO or IGZO, or a compound semiconductor, such as ZnSe, GaAs, InGaAlP or AlInGaN. In this embodiment, the n-type semiconductor layer 144 may be a transparent metal oxide semiconductor, and it may electrically connect with the thin film transistor 16. The light emitting layer 143 of the solid state lighting element 14 is made of CdZnMgSeTe, AlGaInP, AlInGaAs, AlInGaN, ZnO, IGZO, or SiGe.
The thin film transistor 16 is located at a lateral side of the solid state lighting element 14. The thin film transistor 16 includes a gate electrode 161, a source electrode 162, and a drain electrode 163. An insulation layer 160 is formed on the substrate 12. The gate electrode 161 is formed on the insulation layer 160. A gate insulation layer 164 is formed on the gate electrode 161. The gate insulation layer 164 covers the gate electrode 161 therein. The source electrode 162 and the drain electrode 163 are located above the gate electrode 161.
An active layer 165 is formed on the gate insulation layer 164 and is located between the gate electrode 161 and the source electrode 162. The source electrode 162 and the drain electrode 163 are formed on the active layer 165.
The gate insulation layer 164 insulates the gate electrode 161 and the source electrode 162, and also insulates the gate electrode 161 and the drain electrode 163. The thin film transistor 16 can electrically connect with the solid state lighting element 14 by the source electrode 162 or the drain electrode 163.
In the first embodiment, the source electrode 162 or the drain electrode 163 of the thin film transistor 16 electrically connects with the solid state lighting element 14 by the n-type semiconductor layer 144. When the n-type electrode 145 is formed on the n-type semiconductor layer 144, the source electrode 162 or the drain electrode 163 electrically connects with the n-type electrode 145. When the n-type electrode 145 is a metal block, the n-type electrode 145 is formed on the n-type semiconductor layer 144 and is located at a lateral side of the n-type semiconductor layer 144 close to the thin film transistor 16, and the n-type electrode 145 electrically connects with the source electrode 162 or the drain electrode 163. When the n-type electrode 145 is a metal film, and the n-type electrode 145 is formed on the buffer layer 122, the source electrode 162 or the drain electrode 163 extends to connect with the n-type electrode 145.
When the n-type semiconductor layer 144 is a metal oxide semiconductor, the source electrode 162 or the drain electrode 163 electrically connects with the n-type semiconductor layer 144. When the n-type semiconductor layer 144 is a transparent metal oxide semiconductor, the source electrode 162 or the drain electrode 163 electrically connects with the n-type transparent electrode. Such that, the source electrode 162 or the drain electrode 163 may electrically connect with the n-type semiconductor layer 144 or the n-type electrode 145 of the solid state lighting element 14.
The thin film transistor 16 is a poly-silicon thin film transistor or an oxide semiconductor thin film transistor. The active layer 165 of the thin film transistor 16 is a metal oxide semiconductor, a low temperature poly-silicon (LTPS), or an amorphous silicon (a-Si). The metal oxide semiconductor is an amorphous metal oxide semiconductor, poly-silicon metal oxide semiconductor, crystalline metal oxide semiconductor, microcrystalline metal oxide semiconductor, or a nano metal oxide semiconductor. The active layer 165 of the thin film transistor 16 contains In, Ca, Al, Zn, Cd, Ca, Mg, Sn or Pb. Preferably, the active layer 165 is an IGZO (indium gallium zinc oxide) layer. The material for forming the active layer 165 can also be used for forming the current spreading layer 147 of the solid state lighting element 14 which can be transparent.
The gate insulation layer 164 of the thin film transistor 16 can be made of SiOx, SiON, SiNx, HfOx, AlOx, Ta2O5 or BaSrTiOx. At least one of the source electrode 162 and the drain electrode 163 is a transparent oxide electrode, or a metal electrode, or a transparent nonmetallic electrode. The transparent oxide electrode includes ITO (indium tin oxide), IZO (indium zinc oxide), IGZO, AZO (Al-doped Zn Oxide), or ATO (antimony tin oxide). The metal electrode contains one composition of nickel (Ni), titanium (Ti), chromium (Cr), aluminum (Al), gold (Au), silver (Ag), molybdenum (Mo), copper (Cu), platinum (Pt), palladium (Pd), cobalt (Co), tungsten (W), or an alloy thereof. The transparent nonmetallic electrode is made of graphene, carbon nanotubes (CNT) or graphite powder.
According to the first embodiment of the active matrix solid state light display 10, since the solid state lighting element 14 is made of an oxide semiconductor, a nitride semiconductor, a phosphide semiconductor, an arsenide semiconductor or a compound semiconductor, the deterioration problem in manufacturing process is avoided because of the properties of the semiconductors which are not so easily affected by the environmental conditions, and the stability and the reliability of the active matrix solid state light display 10 is maintained.
Alternatively, according to the second embodiment, as shown in
Referring to
The solid state lighting element 24 is a P-N type light emitting diode. The solid state lighting element 24 includes a p-type electrode 241, a p-type semiconductor layer 242, a light emitting layer 243, an oxide semiconductor layer 244 and an n-type electrode 245. In addition, a contact layer 246 and a current spreading layer 247 are located between the p-type semiconductor layer 242 and the p-type electrode 241.
The n-type electrode 245 of the solid state lighting element 24 is a metal film formed on the insulation layer 222 on the substrate 22. The source electrode 262 and the drain electrode 263 are located on the insulation layer 222 on the substrate 22, and are adjacent to the n-type electrode 245. The drain electrode 263 electrically connects with the n-type electrode 245. The oxide semiconductor layer 244 is located on the n-type electrode 245, the source electrode 262, and the drain electrode 263, and covers the n-type electrode 245, the source electrode 262, and the drain electrode 263. In this embodiment, the oxide semiconductor layer 244 and the active layer 265 are formed as a single piece. An gate insulation layer 264 is located on the active layer 265. The gate electrode 261 is located on the gate insulation layer 264.
The light emitting layer 243, the p-type semiconductor layer 242, the contact layer 246, the current spreading layer 247 and the p-type electrode 241 are sequentially formed on the oxide semiconductor layer 244 from a bottom-to-top direction. In this embodiment, the solid state lighting element 24 electrically connects with the thin film transistor 26 by a way of the n-type electrode 245 electrically connecting with the source electrode 262 or the drain electrode 263.
In a fourth embodiment as shown in
The solid state lighting element 24 further includes a phosphor layer 18. The phosphor layer 18 is formed on the solid state lighting element 24. The phosphor layer 18 is formed on the p-type semiconductor layer 242 to form an encapsulation layer, which covers the top of the solid state lighting element 24. The phosphor layer 18 is excited by primary light emitted from the solid state lighting element 24 to emit secondary light with a different color which mixes with the primary light to generate white light.
A color filter (not shown) can also be provided to be located on the phosphor layer 18 to filter the white light into light of different colors, such as red light, green light and blue light.
The solid state lighting element 24 may emit ultraviolet light, blue light, blue-green light, green light or red light, matching with the colors of the phosphor layer 18. Preferably, the solid state lighting element 24 emits blue light to match with the phosphor layer 18 having green and red fluorescent powder therein; or the solid state lighting element 24 emits ultraviolet light to match with the phosphor layer 18 having red, green and blue fluorescent powder therein.
The phosphor layer 18 may be a plate 182, and the plate 182 is located at an outer side of the solid state light display 20. For example, the plate 182 is located at a same side with the solid state lighting element 24, or two plates 182 which are located at opposite sides of the substrate 22. That is, the plate 182 is located on a light path of the solid state light display 20 and separated from the solid state light display 10 to form a remote phosphor structure.
According to the active matrix solid state light display in this disclosure, because of the material properties of the solid state lighting element, the problem of degradation of organic materials in the manufacturing process of solid state light display can be effectively solved, and the stability of the solid state light display is maintained, and the service life is also extended.
It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102111280 | Mar 2013 | TW | national |
