在本文中，以氮化鋁鎵/氮化鎵單一量子井結構之金屬-半導體-金屬光檢測器將被製作並探討其特性。此結構之光檢測器將與傳統以未摻雜氮化鎵為主動層之光檢測器作比較。為了抑制光檢測器之漏電流，低溫成長之氮化鎵薄膜將被覆蓋在兩種結構上。單一量子井結構之光檢測器在光暗電流比及響應的拒斥比上都未如傳統結構來得好；但響應之最大值與其對應的量子效率較傳統結構有明顯的提昇。其響應之最大值為 0.0496 A/W , 對應之量子效率為 17.08 %。
另外，我們將改變量子井的成長方式，以將氮化鋁鎵中鋁的含量以漸變的方式成長。所得之量子井形狀為三角形之結構，將其製作為金屬-半導體-金屬光檢測器，並與一般形狀之量子井作比較。使用三角形量子井結構之光檢測器在響應以及量子效率方面將有小幅度的改善。
在傳統結構之金屬-半導體-金屬光檢測器中，我們也試著改變覆蓋層的材料來製作。將採用較高能隙之氮化鋁來作為覆蓋層。我們將可以發現其暗電流有明顯降低的情形，這是因為在表面的有效蕭基能障將可以被提高。而在光激發以及響應特性上面並無負面之影響。

In this thesis, AlGaN/GaN single-quantum-well (SQW) metal-semiconductor-metal (MSM) photodetector is successfully fabricated and analyzed. We will compare the optical characteristics of SQW photodetector and conventional u-GaN photodetector. In order to suppress the leakage current, the low-temperature (LT) grown GaN cap layer is used on both structures. Although the photocurrent to dark current ratio and spectral responsivity rejection ratio of SQW photodetector is not as good as the conventional one, the peak responsivity and quantum efficiency will be improved. The peak responsivity is 0.0496 A/W, and the corresponded quantum efficiency is 17.08%.
We also change the growth of the QW, in which the AlGaN barrier will be grown by changing the content of AlGaN in graded. And then we will obtain the Triangular-shaped QW and fabricate the MSM photodetector. The peak responsivity and quantum efficiency will be a little improved in Triangular-shaped QW than in Square-shaped QW photodetector.
On the other hand, we change the cap layer in the conventional u-GaN MSM photodetector. We adopt LT-AlN as the cap layer, which has higher bandgap energy. By using LT-AlN as the cap, the dark current of photodetector will be obviously decreased. This is due to the lowering of Schottky barrier height. The spectral responsivity will not be changed.

Reference

[1] M. A. Khan, J. N. Kuznia, A. R. Bhattarai and D. T. Oslon, “Metal-semiconductor field effect transistor based on single crystal GaN”, Appl. Phys. Lett. Vol. 62, p. 1786 (1993)

[2] T. Mukai, H. Narimatsu, and S. Nakamura, “Amber InGaN-Based Light-Emitting Diodes Operable at High Ambient Temperatures”, Jpn. J. Appl. Phys. Vol. 37, p. L479 (1998)

[3] S. Nakamura, M. Senoh, N. Iwasa, S. Nagahama, T. Yamada and T. Mukai, “Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes”, Jpn. J. Appl. Phys. Vol. 34, p. L1332 (1995)

[4] T. Mukai, D. Morita and S. Nakamura, “High-power UV InGaN/AlGaN double-heterostructure LEDs”, J. Cryst. Growth, Vol. 190, p. 778 (1998)

[5] Z. C. Huang, D. B. Mott, P. K. Shu, R. Zhang, J. C. Chen and D. K. Wickenden, “Optical quenching of photoconductivity in GaN photoconductors”, J. Appl. Phys. Vol. 82, p. 2707 (1997)

[6] J. C. Carrano, T. Li, P. A. Grudowski, C. J. Eiting, R. D. Dupuis and J. C. Campell, “Comprehensive characterization of metal – semiconductor - metal ultraviolet photodetectors fabricated on single-crystal GaN”, J. Appl. Phys. Vol. 83, p. 6148 (1998)

[7] D. Walker, E. Monroy, P. Kung, J. Wu, M. Hamilton, F. J. Sanchez, J. Diaz and M. Razeghi, “High-speed, low-noise metal-semiconductor-metal ultraviolet photodetectors based on GaN”, Appl. Phys. Lett. Vol. 74, p. 762 (1999)

[8] E. Monroy, F. Calle, E. Munoz and F. Omnes, “Effects of Bias on the Responsivity of GaN Metal-Semiconductor-Metal Phodiodes”, Phy. Stat. Sol.(a),Vol.176, p.157 (1999)

[9] Egawa, T. Jimbo and M. Umeno, “Back-Illuminated GaN Metal-Semiconductor-Metal UV Photodetector with High Internal Gain”, Jpn. J. Appl. Phys. Vol. 40, p. L505 (2001)

[10] C. H. Chen, S. J. Chang, Y. K. Su, G. C. Chi, J. Y. Chi, C. A. Chang, J. K. Sheu and J. F. Chen, “GaN metal-semiconductor-metal ultraviolet photodetectors with transparent indium-tin-oxide Schottky contacts”, IEEE photon. Technol. Lett. Vol. 13, p. 848 (2001)

[11] E. H. Rhoderick and R. H. Williams, “Metal-Semiconductor Contacts”, Clarendon Press, Oxford (1998)

[12] S. M. Sze, Semiconductor Device Physics and Technology, p. 160,278 (1985) WANG and E. KUOKSTIS, “III–Nitride UV Devices”, Japanese Journal of Applied Physics Vol. 44, No. 10, pp. 7191–7206, (2005)

[13] Y.K. Su , P.C. Chang , C.H. Chen , S.J. Chang ,*, C.L. Yu , C.T. Lee ,H.Y. Lee , J. Gong , P.C. Chen , C.H. Wang,” Nitride-based MSM UV photodetectors with photo-chemical annealing Schottky contacts”, Solid-State Electronics Vol. 49, p. 459–463, (2005)

[14] EMonroy, F Omn`es and F Calle, “Wide-bandgap semiconductor ultraviolet photodetectors”, Semicond. Sci. Technol. Vol.18, p. R33–R51 (2003)

[15] R. J. Choi,Y. B. Hahn, H. W. Shim, M. S. Han, E. K. Suh, and H. J. Lee, “Efficient blue light-emitting diodes with InGaN/GaN triangular shaped multiple quantum wells”, Appl. Phys. Lett. Vol. 82, No.17, (2003)

[16] M.L. Lee, J.K. Sheu, W.C. Lai, S.J. Chang, and Y.K. Su, “GaN Schottky barrier photodetectors with a low-temperature GaN cap layer”, Appl. Phys. Lett. Vol. 82, No.17, (2003)

[17] M. Mikulics, M. Marso, P. Javorka, P. Kordos, and H. Luth, “Ultrafast metal-semiconductor-metal photodetectors on low-temperature-grown GaN”, Appl. Phys. Lett. Vol. 86, No.211110, (2005)

[18] C. Rivera, J.L. Pau, J. Pereiro, E. Munoz, “Properties of Schottky barrier photodiodes based onInGaN/GaN MQW structures”, Superlattices and Microstructure, Vol. 36, p.849-p.857, (2004)

[19] S. Noor Mohammad, “Contact mechanisms and design principles for Schottky contacts to group-III nitrides”, Journal of Applied Physics, Vol. 97, No.063703, (2005)

[20] A. Teke, S. Dogan, F. Yun, M.A. Reshchikov, H. Le, X.Q. Liu,
H. Morkoc, S.K. Zhang, W.B. Wang, R.R. Alfano, “GaN/AlGaN back-illuminated multiple-quantum-wellSchottky barrier ultraviolet photodetectors”,Solid-State Electrons, Vol. 47, p.1401-p.1408, (2003)

[21] J. C. Carrano, T. Li, P. A. Grudowski, C. J. Eiting, R. D. Dupuis, and J.C.Campbell, “Current transport mechanisms in GaN-based metal–semiconductor–metal photodetectors”, Appl. Phys. Lett., Vol. 72, No.5, p.2, (1998)

[22] C. H. Chen, S. J. Chang, Y. K. Su, G. C. Chi, J. Y. Chi, C. A.
Chang, J. K. Sheu and J. F. Chen, “GaN metal-semiconductor-metal ultraviolet photodetectors with transparent indium-tin-oxide Schottky contacts”, IEEE photon.Technol. Lett. Vol. 13, p. 848 (2001)

[23] H. Z. Xu, Z. G. Wang, M. Kawabe, I. Harrison, B. J. Ansell and C.
T.Foxon, “Fabrication and characterization of metal-semiconductor-metal (MSM) ultraviolet photodetectors on undoped GaN/sapphire grown by MBE”, J. Cryst. Growth, Vol.218, p. 1 (2000)

[24] S.Y. Kwon, M. H. Cho, P. Moon1, H. J. Kim, H. Na1, H.C. Seo1, H. J. Kim, Y. Shin,D. W. Moon, Y. Sun, Y.-H. Cho, and E. Yoon, “Near-UV emission from In-rich InGaN/GaN single quantum well structure with compositional grading”, Phys. Stat. Sol.(a), Vol. 201, No.12, p.2818-p.2822, (2004)