1. Use the same contacts for GaN based UV Photodetectors Y.C. Chiang

2. Outline IntroductionIntroduction ExperimentsExperiments Results and discussionResults and discussion ConclusionConclusion ReferencesReferences

3. ITON Schottky contacts for GaN based UV photodetectors N. Vanhove, J. John, A. Lorenz, K. heng, N. Vanhove, J. John, A. Lorenz, K. heng, G. Borghs, J.E.M. Haverkort G. Borghs, J.E.M. Haverkort

4. Introduction Due to the low transmission of UV light in the metal layers, transparent oxides like ITON should improve sensitivity of the photodetector.Due to the low transmission of UV light in the metal layers, transparent oxides like ITON should improve sensitivity of the photodetector. In spectroscopic measurements, ITON has shown an improved UV transmission.In spectroscopic measurements, ITON has shown an improved UV transmission.

5. Experiments 20/40/25/50 nm 100 nm Fig. 1. Schematic cross section of a Schottky UV photodiode.

6. Results and discussion Fig. 2. I–V characteristic of an ITON/GaN Schottky diode (dark and under UV illumination).

7. Results and discussion Fig. 3. Spectral responsivity of a typical ITON/GaN photodiode at bias of -1 V. 30 A/W

8. Results and discussion Fig. 4. C–V measurement of an ITON/GaN Schottky diode under dark conditions and under UV illumination.

9. Results and discussion Fig. 5. Transient behavior of the UV response of an ITON/GaN Schottky-Barrier diode at a bias voltage of -1 V.

10. Conclusion Photodetectors with excess photocurrent showed the effect of persistent photocurrent when UV light was switched off.Photodetectors with excess photocurrent showed the effect of persistent photocurrent when UV light was switched off.

11. References N. Vanhove, J. John, A. Lorenz, K. Cheng, G. Borghs, J.E.M. Haverkort, ITON Schottky contacts for GaN based UV photodetectors, Appl. Surf. Sci., 253(5), 2930-2932, (2006) N. Vanhove, J. John, A. Lorenz, K. Cheng, G. Borghs, J.E.M. Haverkort, ITON Schottky contacts for GaN based UV photodetectors, Appl. Surf. Sci., 253(5), 2930-2932, (2006)

12. Gallium nitride photoconductive ultraviolet sensor with a sputtered transparent indium- tin-oxide ohmic contact Y.C. Jiang

13. Outline IntroductionIntroduction Experimental detailsExperimental details Results and discussionResults and discussion ConclusionsConclusions ReferencesReferences

14. Introduction The reasonably large Schottky barrier height at ITO/n-GaN interface also suggests ITO could be used as the contact electrodes of GaN-based MSM photodetectors.The reasonably large Schottky barrier height at ITO/n-GaN interface also suggests ITO could be used as the contact electrodes of GaN-based MSM photodetectors.

15. Experimental details Fig. 1. A designed MSM pattern with two interdigitated electrodes.

16. Experimental details Fig. 2. The optical transmittance as a function of wavelength for ITO films.

17. Experimental details Fig. 3. The I –V curves of the ITO/n-GaN samples with as- deposited, 500 and 600 -C annealing conditions.

18. Results and discussion Fig. 4. The dark and illuminated I –V characteristics of as-deposited ITO MSM photoconductors on GaN.

19. Results and discussion Fig. 5. Photo-responsivity of as-deposited ITO MSM photoconductor on GaN. 327 A/W

20. Conclusions ITO layers were deposited onto n-GaN films by RF sputtering. The deposited ITO became more transparent after proper annealing and formed good ohmic contacts on n-GaN. ITO layers were deposited onto n-GaN films by RF sputtering. The deposited ITO became more transparent after proper annealing and formed good ohmic contacts on n-GaN.

21. References J.D. Hwang and C.C. Lin, “Gallium nitride photoconductive ultraviolet sensors with a sputtered transparent indium-tin-oxide ohmic contact”, Thin Solid Films, 491, pp.276-279, 2005. J.D. Hwang and C.C. Lin, “Gallium nitride photoconductive ultraviolet sensors with a sputtered transparent indium-tin-oxide ohmic contact”, Thin Solid Films, 491, pp.276-279, 2005.