Photon source and a method of fabricating a photon source

Abstract

A photon source, comprising: a semiconductor structure, said semiconductor structure comprising: a first light emitting diode region; and a second region comprising a quantum dot; the photon source further comprising: a first voltage source configured to apply an electric field across said first light emitting diode region to cause light emission; a second voltage source configured to apply a tuneable electric field across said second region to control the emission energy of said quantum dot; wherein the semiconductor structure is configured such that light emitted from said first light emitting diode region is absorbed in said second region and produces carriers to populate said quantum dot; and wherein the photon source is configured such that light emitted from the second region exits said photon source.

1 . A photon source, comprising:
 a semiconductor structure, said semiconductor structure comprising:
 a first light emitting diode region; and 
 a second region comprising a quantum dot; 
   
       the photon source further comprising:
 a first voltage source configured to apply an electric field across said first light emitting diode region to cause light emission by spontaneous emission; 
 a second voltage source configured to apply a tuneable electric field across said second region to control the emission energy of said quantum dot; 
 
       wherein the semiconductor structure is configured such that light emitted from said first light emitting diode region is absorbed in said second region and produces carriers to populate said quantum dot; and 
       wherein the photon source is configured such that light emitted from the second region exits said photon source. 
     
     
         2 . The photon source according to  claim 1 , wherein the semiconductor structure comprises a substrate, and wherein the first light emitting diode region and the second region are monolithically integrated with the substrate. 
     
     
         3 . The photon source according to  claim 1 , wherein the energy of the light emitted from the first light emitting diode region is greater than the energy of the light emitted from the second region. 
     
     
         4 . The photon source according to  claim 3 , wherein the features of the absorption spectrum as a function of wavelength of the second region are substantially matched to the features of the emission spectrum of the first region. 
     
     
         5 . The photon source according to  claim 1 , wherein the semiconductor structure further comprises:
 one or more further regions, each comprising a quantum dot;   
       wherein the photon source further comprises:
 a voltage source, configured to apply a tuneable electric field across each further region to control the emission energy of said quantum dots; 
 
       wherein the semiconductor structure is configured such that light emitted from said first light emitting diode region impacts said further regions and produces carriers to populate said quantum dot; and 
       wherein the photon source is configured such that light emitted from the further regions exits said photon source. 
     
     
         6 . The photon source according to  claim 1 , wherein the second region is arranged at least partly around the first light emitting diode region. 
     
     
         7 . The photon source according to  claim 1 , wherein the second region further comprises a plurality of quantum dots, wherein light emitted from said first light emitting diode region produces carriers to populate said quantum dots. 
     
     
         8 . The photon source according to  claim 1 , wherein the first light emitting diode region is arranged overlying the second region. 
     
     
         9 . The photon source according to  claim 8 , wherein the second region is integrated with a waveguiding region. 
     
     
         10 . The photon source according to  claim 1 , wherein the second voltage source is a DC voltage source. 
     
     
         11 . The photon source according to  claim 1 , wherein the first voltage source is configured to apply a time varying electric field to the first light emitting diode region. 
     
     
         12 . The photon source according to  claim 1 , wherein said photon source is configured such that the electric field is tuneable across an operating range having an upper limit of 100 KVcm −1 . 
     
     
         13 . The photon source according to  claim 12 , wherein the tunnelling time of carriers from said quantum dot is greater than the radiative decay time of an exciton in said quantum dot over said operating range. 
     
     
         14 . The photon source according to  claim 1 , wherein said quantum dot comprises a neutral exciton, bi-exciton or higher order exciton, and wherein the field applied across the second region is configured to minimise fine structure splitting. 
     
     
         15 . The photon source according to  claim 1 , further comprising a waveguide region configured to guide light emitted from the first light emitting diode region to the second region. 
     
     
         16 . The photon source according to  claim 1 , wherein the first region and second region share an electrical contact region of a first type and each have a separate electrical contact region of a second type . 
     
     
         17 . The photon source according to  claim 1 , further comprising an optical cavity region, wherein the quantum dot is located in and is spectrally resonant with the optical cavity region. 
     
     
         18 . The photon source according to  claim 1 , wherein the light emitted from said first light emitting diode region consists of spontaneous photons that are not amplified by stimulated emission. 
     
     
         19 . The photon source according to  claim 1 , the second region further comprising at least one barrier layer. 
     
     
         20 . A method of fabricating a photon source, comprising the steps of:
 i) forming a semiconductor structure, comprising a first light emitting diode region and a second region comprising a quantum dot, on a semiconductor substrate, wherein the semiconductor structure is configured such that light emitted from said first light emitting diode region impacts said second region and produces carriers to populate said quantum dot and wherein the photon source is configured such that light emitted from the second region exits said photon source;   ii) electrically coupling a first voltage source to the first light emitting diode region, the first voltage source configured to apply an electric field across said first light emitting diode region to cause light emission by spontaneous emission;   iii) electrically contacting a second voltage source to the second region, the second voltage source configured to apply a tuneable electric field across said second region to control the emission energy of said quantum dot.