E-MRS 2006 Spring Meeting (E-MRS), May 29 to June 2, 2006, Nice, France.

Al Schottky contact on p-GaSe

Wen-Chang Huang, Shui-Hsiang Su1, Yu-Kuei Hsu2, Chih-Chia Wang3, Chen-Shiung Chang2

半導體元件研究室

Abstract-- A new Schottky diode, Al/p-GaSe was presented at this study. It shows an effective barrier height of 0.96 eV with an ideality factor of 1.24 last over five decades and a reverse leakage current density of 4.1210-7 A/cm2 at -2V after rapid thermal annealing at 400C for 30 sec. The generation-recombination effect of the Schottky diode was decreased as the annealing temperature was increased. The formation of Al1.33Se2 was observed by X-ray diffraction analysis after the thermal annealing at 400C for 30 sec. A rougher surface morphology of the contact was observed both by AFM and SEM, as the annealed temperature was increased.

Introduction--gallium selenide (GaSe) are known to present outstanding nonlinear optical properties. Their refractive index anisotropy makes them suitable for second harmonic generation,[1] parametric oscillation,[2] and frequency mixing[3] in the middle infrared spectral zone where they are transparent. It also has a relatively large band gap energy of 2.0 eV, so it is potential applications to realized visible light emitter diode.[4] The Gallium selenide crystal was also used as material for nuclear particle detectors.[5] In order to attain devices such as light emitter diode or nuclear particle detector with acceptable characteristics, high quality metal contacts to GaSe are necessary.

Experiments--The p-type Er:GaSe crystals used in this study were obtained by the Bridgmann method. The carrier concentration of the GaSe:Er crystal is 1.531017cm-3 and resistivity is 1.199 -cm. Thermal evaporator was used to deposit aluminum on the front surface of GaSe substrate. The thickness of the aluminum is 100nm. After metal deposition, the samples were treated by rapid thermal annealing (RTA) at 200C, 300C and 400C, respectively for 30 sec. The ohmic contact on the back side of GaSe substrate was then formed by soldering high-purity indium.

Results and discussions—

The effective Schottky barrier height--is 0.99eV, 0.98eV and 0.96eV for the as deposited, 300C-annealed, and 400C-annealed contacts, respectively.

The ideality factor--of the as-deposited contact is 2.1, of the 300C-annealed contact is 1.84 and of the 400C-annealed contact is 1.24.

The reverse leakage current density--is equal to 5.7310-4 A/cm2 , 9.2810-5 A/cm2 and 6.410-6 A/cm2 for the as deposited, 300C-annealed and 400C-annealed, respectively, at -3V.

The XRD--analysis of the Al/p-GaSe diode before and after thermal annealing, respectively.

The AFM pictures-- RMS value is equal to 1.56, 2.74 and 2.87 for the as deposited diode, 300C-annealed diode and 400C-annealed diode, respectively.

The SEM pictures-- of the as deposited diode, the 300C-annealed diode, and the 400C-annealed diode, respectively.

Conclusion--A new Schottky diode, Al/p-GaSe was realized in the research. It shows a effective barrier of 0.94eV with an ideality factor of 1.24 at the 400C annealed diode. The contact interface of the diode was passivated after thermal annealing. The passivation gave rise to a lower reverse leakage current and a better ideality factor. A new phase of Al1.33Se2 was formed and the surface became rough after the thermal annealing.

Acknowledgments--The authors would like to thank the National Science Council of the Republic of China, for financially supporting the research under Contract No. NSC-94-2216-E- 168- 004.

References--[1] E. Bringuier, A. Bourdon, N. Piccioli, and A. Chevy, Phys. Rev. B, 49 (1994) 16971.[2] K. L. Vodopyanov, L. A. Kulewskii, V. G. Voevodin, A. Y. Gribenyukov, K. R. Allakhverdiev, and T. A. Terimov, Opt. Commun., 83 (1991) 322.[3] A. Bianchi, A. Ferrario, and M. Mucsi, Opt. Commun. 25 (1978) 256.[4] M. Budiman, Tamotsu Okamoto, Akira Yanada and Makoto Konagai, Jpn. J. Appl. Phys., 37 (1998) 5497.[5] Sakai, H. Nakatani, C. Tatsuyama and F. Takeda, IEEE Tran. on Nucl. Sci., 35 (1988) 85.