Multi-color light emitting devices with compositionally graded cladding group iii-nitride layers grown on substrates

Abstract

A light emitting device includes a substrate, multiple n-type layers, and multiple p-type layers. The n-type layers and the p-type layers each include a group III nitride alloy. At least one of the n-type layers is a compositionally graded n-type group III nitride, and at least one of the p-type layers is a compositionally graded p-type group III nitride. A first ohmic contact for injecting current is formed on the substrate, and a second ohmic contact is formed on a surface of at least one of the p-type layers. Utilizing the disclosed structure and methods, a device capable of emitting light over a wide spectrum may be made without the use of phosphor materials.

1 . A light emitting device capable of emitting light, comprising:
 a substrate;   a plurality of n-type layers, each comprising a group III nitride alloy, wherein said plurality of n-type layers comprise at least one layer of n-type graded group III nitride;   a plurality of p-type layers, each comprising a group III nitride alloy, wherein said plurality of p-type layers comprise at least one layer of p-type graded group III nitride;   a first ohmic contact for injecting current formed on the substrate; and   a second ohmic contact formed on a surface of at least one of the layers.   
     
     
         2 . The light emitting device according to  claim 1 , wherein an alloy composition and/or the thickness of an InGaN p/n junction is adjusted to optimize the intensity and to select the wavelength of the emitted light. 
     
     
         3 . The light emitting device according to  claim 1 , wherein the Group III Nitride alloy comprises InGaN. 
     
     
         4 . The light emitting device according to  claim 1 , wherein the Group III Nitride alloy comprises an InAlN ternary alloy. 
     
     
         5 . The light emitting device according to  claim 1 , wherein the Group III Nitride alloy comprises an InGaAlN quaternary alloy. 
     
     
         6 . The light emitting device according to  claim 1 , wherein the substrate comprises Silicon. 
     
     
         7 . The light emitting device according to  claim 6 , wherein the substrate comprises a doped P-type Silicon substrate. 
     
     
         8 . The light emitting device according to  claim 1 , wherein the substrate comprises sapphire. 
     
     
         9 . The light emitting device according to  claim 1 , wherein the substrate comprises Silicon Carbide. 
     
     
         10 . The light emitting device according to  claim 1 , wherein said wide spectrum is from ultra-violet to near-infrared. 
     
     
         11 . The light emitting device according to  claim 1 , wherein a p/n junction is formed in InGaN of a target composition. 
     
     
         12 . The light emitting device according to  claim 1 , wherein a p/n junction is formed in a compositionally graded n-type region. 
     
     
         13 . A light emitting device based on group III-nitride semiconductors grown on a Silicon substrate capable of emitting light over a wide spectrum, from ultra-violet to near-infrared, said light-emitting device comprising one or more p-type compositionally graded group III nitride layers and one or more n-type compositionally graded group III nitride layers. 
     
     
         14 . A light emitting device comprising:
 a heavily doped p-type Si substrate;   a buffer layer formed on the p-type Si substrate;   an n-type GaN layer formed on the buffer layer;   a compositionally graded n-type InGaN layer formed on n-type GaN layer and graded from GaN to a target InGaN composition having a desired percentage of In;   an n-type InGaN layer formed on the compositionally graded n-type InGaN layer and a p-type InGaN layer formed on the n-type InGaN layer, wherein the n-type and p-type InGaN layers comprise the target InGaN composition and form the p/n junction;   a graded p-type InGaN layer formed on p-type InGaN layer and graded from the target InGaN composition to GaN;   a p-type GaN layer formed on the graded p-type InGaN layer;   an ohmic contact for injecting current; and   a top ohmic contact formed on a surface of one of the layers.   
     
     
         15 . The light emitting device according to  claim 14 , wherein the buffer layer comprises a nucleation layer. 
     
     
         16 . The light emitting device according to  claim 14 , wherein the nucleation layer comprises a thin AlN nucleation layer.