Use the same contacts for GaN based UV Photodetectors

Y.C. ChiangY.C. Chiang

Outline

• IntroductionIntroduction

• ExperimentsExperiments

• Results and discussionResults and discussion

• ConclusionConclusion

• ReferencesReferences

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

Introduction

• Due to the low transmission of UV light in tDue to the low transmission of UV light in the metal layers, transparent oxides like ITOhe metal layers, transparent oxides like ITON should improve sensitivity of the photodeN should improve sensitivity of the photodetector.tector.

• In spectroscopic measurements, ITON has sIn spectroscopic measurements, ITON has shown an improved UV transmission.hown an improved UV transmission.

Experiments

20/40/25/50 nm

100 nm

Fig. 1. Schematic cross section of a Schottky UV photodiode.

Results and discussion

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

Results and discussion

Fig. 3. Spectral responsivity of a typical ITON/GaN photodiode at bias of -1 V.

30 A/W

Results and discussion

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

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.

Conclusion

• Photodetectors with excess photocurrent shPhotodetectors with excess photocurrent showed the effect of persistent photocurrent wowed the effect of persistent photocurrent when UV light was switched off.hen UV light was switched off.

References N. Vanhove, J. John, A. Lorenz, K. Cheng, G. N. Vanhove, J. John, A. Lorenz, K. Cheng, G.

Borghs, J.E.M. Haverkort, ITON Schottky coBorghs, J.E.M. Haverkort, ITON Schottky contacts for GaN based UV photodetectors, Apntacts for GaN based UV photodetectors, Appl. Surf. Sci., 253(5), 2930-2932, (2006)pl. Surf. Sci., 253(5), 2930-2932, (2006)

Gallium nitride photoconductive ultraviolet sensor with a sputtered transparent indium-t

in-oxide ohmic contact

Y.C. JiangY.C. Jiang

Outline

• IntroductionIntroduction

• Experimental detailsExperimental details

• Results and discussionResults and discussion

• ConclusionsConclusions

• ReferencesReferences

Introduction

• The reasonably large Schottky barrier heighThe reasonably large Schottky barrier height at ITO/n-GaN interface also suggests ITO t at ITO/n-GaN interface also suggests ITO could be used as the contact electrodes of Gcould be used as the contact electrodes of GaN-based MSM photodetectors.aN-based MSM photodetectors.

Experimental details

Fig. 1. A designed MSM pattern with two interdigitated electrodes.

Experimental details

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

Experimental details

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

Results and discussion

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

Results and discussion

Fig. 5. Photo-responsivity of as-deposited ITO MSM photoconductor on GaN.

327 A/W

Conclusions

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

References

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