Semiconductor light emitting device and method for manufacturing the same

Abstract

A semiconductor light emitting device is provided with a GaAs substrate, a quantum dot active layer formed over the GaAs substrate, a GaAs layer formed above or below the quantum dot active layer, and a diffraction grating formed from InGaP or InGaAsP and periodically provided along an propagating direction of light in the GaAs layer.

1 . A semiconductor light emitting device comprising:
 a GaAs substrate;   a quantum dot active layer formed over the GaAs substrate;   a GaAs layer formed above or below the quantum dot active layer; and   a diffraction grating formed from InGaP or InGaAsP and periodically provided along an propagating direction of light in the GaAs layer.   
     
     
         2 . The semiconductor light emitting device as claimed in  claim 1 , further comprising an n-type cladding layer, wherein the GaAs layer is provided between the quantum dot active layer and the n-type cladding layer. 
     
     
         3 . The semiconductor light emitting device as claimed in  claim 1 ,
 wherein the GaAs layer is formed above the quantum dot active layer;   further comprising a ridge structure including the GaAs layer.   
     
     
         4 . The semiconductor light emitting device as Claimed in  claim 2 , further comprising a ridge structure including the n-type cladding layer. 
     
     
         5 . The semiconductor light emitting device as claimed in  claim 1 , wherein the GaAs layer is an n-type GaAs layer, and the diffraction grating is formed from n-type InGaP or n-type InGaAsP. 
     
     
         6 . The semiconductor light emitting device as claimed in  claim 1 , further comprising a current blocking layer provided above or below the GaAs layer, the current blocking layer being formed from AlAs or AlGaAs. 
     
     
         7 . The semiconductor light emitting device as claimed in  claim 1 , further comprising an upper cladding layer and a lower cladding layer, wherein the upper cladding layer and the lower cladding layer are formed from one of semiconductor materials of the group consisting of AlGaAs, InGaP, and InGaAsP. 
     
     
         8 . The semiconductor light emitting device as claimed in  claim 2 , wherein the n-type cladding layer is formed from one of semiconductor materials of the group consisting of AlGaAs, InGaP, and InGaAsP. 
     
     
         9 . The semiconductor light emitting device as claimed in  claim 1 , wherein the quantum dot active layer includes quantum dots formed from one of semiconductor materials of the group consisting of InAs, InAsSb, InNAs, and InNAsSb. 
     
     
         10 . The semiconductor light emitting device as claimed in  claim 1 , wherein the quantum dot active layer includes in a part thereof p-type impurities. 
     
     
         11 . The semiconductor light emitting device as claimed in  claim 2 , further comprising:
 a p-type cladding layer; and   a ridge structure including the p-type cladding layer.   
     
     
         12 . The semiconductor light emitting device as claimed in  claim 11 , further comprising a current blocking layer provided to be sandwiched with the p-type cladding layer, or provided between the p-type cladding layer and the quantum dot active layer, the current blocking layer being formed from AlAs or AlGaAs. 
     
     
         13 . The semiconductor light emitting device as claimed in  claim 11 , wherein the p-type cladding layer is formed from one of semiconductor materials of the group consisting of AlGaAs, InGaP, and InGaAsP. 
     
     
         14 . The semiconductor light emitting device as claimed in  claim 1 , wherein the GaAs substrate is one of substrates of the group consisting of a p-type conductive substrate, an n-type conductive substrate, and a high resistance substrate. 
     
     
         15 . A method for manufacturing a semiconductor light emitting device comprising:
 forming a lower cladding layer over a GaAs substrate;   forming a quantum dot active layer over the lower cladding layer;   forming a first semiconductor layer over the quantum dot active layer;   forming a diffraction grating by etching the first semiconductor layer;   forming a second semiconductor layer burying the diffraction grating; and   forming an upper cladding layer having a conductive type different from that of the lower cladding layer over the second semiconductor layer,   wherein the processes after forming the quantum dot active layer are performed at a temperature not thermally deteriorating or degrading quantum dots included in the quantum dot active layer.   
     
     
         16 . The method for manufacturing a semiconductor light emitting device as claimed in  claim 15 , further comprising:
 forming, as the first semiconductor layer, an InGaP layer or InGaAsP layer;   forming, as the diffraction grating, an InGaP diffraction grating or an InGaAsP diffraction grating by etching the InGaP layer or the InGaAsP layer; and   forming, as the second semiconductor layer, a GaAs guide layer burying the InGaP diffraction grating or the InGaAsP diffraction grating.   
     
     
         17 . The method for manufacturing a semiconductor light emitting device as claimed in  claim 16 , further comprising:
 forming a GaAs layer over the InGaP layer or the InGaAsP layer after forming the first semiconductor layer and before forming the diffraction grating;   forming, as the diffraction grating, an InGaP diffraction grating or an InGaAsP diffraction grating having a GaAs cap layer in an upper part thereof by etching the GaAS layer and the InGaP layer or the InGaAsP layer; and   forming, as the second semiconductor layer, the GaAS guide layer by growing a GaAs buried layer such that the InGaP diffraction grating or the InGaAsP diffraction grating having the GaAs cap layer in an upper part thereof is buried.   
     
     
         18 . The method for manufacturing a semiconductor light emitting device as claimed in  claim 15 , wherein the processes after forming the quantum dot active layer are performed at a temperature of 630° C. or less.