1. Radiative efficiency of light-emitting materials Tim Gfroerer Davidson College, Davidson, NC - Funded by Research Corporation and the Petroleum Research Fund A talk given at the SPIE Regional Meeting on Optoelectronics, Photonics, and Imaging (2000)

2. Outline  Motivation  Experimental technique  Material system: InGaAs  Conclusion

3. Motivation laser diodes light-emitting diodes  light is good!  heat is bad!

4. Motivation (continued) collection efficiency = ? internal reflection scattering refraction reabsorption

5. Measuring the efficiency light in heat signal  light out light in = heat + light out  T  heat efficiency = light in / light out

6. Experimental set-up light in light out - heat

7. Efficiency calibration increasing excitation excitation  light + heat

8. Calibrated efficiency defects light Auger

9. Nonradiative mechanisms defects:Auger:

10. GaInAs bandgap GaAs InAs InP substrate Ga 0.5 In 0.5 As

11. Lattice mismatch misfit dislocations and strain

12. Auger activation Conduction band Valence band energy momentum EaEa smaller E a smaller bandgap:

13. Conclusions  New radiative efficiency measurement technique  Material system: InGaAs  Recombination and Lattice mismatch