|AVS 62nd International Symposium & Exhibition|
|Electronic Materials and Processing||Thursday Sessions|
|Session:||III-N Nitrides for Optoelectronic Applications|
|Presenter:||Sami Bolat, Bilkent University, Turkey|
|Authors:||B. Tekcan, Bilkent University, Turkey
S. Bolat, Bilkent University, Turkey
C. Ozgit-Akgun, Bilkent University, Turkey
N. Biyikli, Bilkent University, Turkey
A.K. Okyay, Bilkent University, Turkey
|Correspondent:||Click to Email|
For many electronic and optical applications, III-nitride materials are much sought after due to their direct and high optical band-gap, high electron saturation velocity and band-gap tunability . These important features enable many possible device applications, which are generally used in high power and high frequency applications . However, these films are generally grown using high temperature and high vacuum processes namely, MOCVD , MBE  which limit substrate selection along with CMOS compatibility. In our work, we offer an alternative way of growth to fabricate thin film transistors (TFTs) and UV metal-semiconductor-metal (MSM) photodetectors. Hollow cathode plasma assisted Atomic Layer Deposition (HC-PA-ALD) technique make low temperature device applications possible. We have grown GaN and InGaN films and analyzed TFT and photodetector properties in detail. Electrical and optical characteristics of these devices are inspected.
The results can pave the way for ALD to be used for III-Nitride based electronic and optical devices. Thin film transistor exhibit 2x103 ON/OFF ratio with threshold voltage of 11.8 V. Metal-semiconductor-metal (MSM) photodetectors, on the other hand, showed 20 pA under -20 V voltage bias with a UV responsivity of 680 m A/W under 290 nm incident light with only a 20 nm thick film. Effect of annealing on the device performance is also studied. TFTs ON/OFF ratio increased to 2x104 with a lower threshold voltage and contact resistance decreased 4000 times when annealed at 800 °C for 30 seconds. Moreover, MSM devices performance also enhanced after annealing 600 °C. The photoresponsivity as high as 950 m A/W at 290 nm incident light is recorded. The dark current reduced significantly, a current value of 50 fA is recorded under -20 V voltage bias.
Along with GaN devices, InGaN based photodetectors are fabricated and characterized. MSM devices based on InGaN devices showed responsivity and dark current levels controlled by In concentration. The resistivity of the films decreased with concentration of In in the semiconductor. Changing the In concentration, bandgap tunability is possible.
 A. Krost and A. Dadgar, Phys. State Solidi A 194, 361 (2002).
 J. S. Moon, M. Micovic, P. Janke, P. Hashimoto, W. S. Wong, R. D.Widman, L. McCray, A. Kurdoghlian, and C. Nguyen, Electron. Lett. 37, 528 (2001).
 S. Nakamura, Y. Harada, and M. Seno, Appl. Phys. Lett. 58, 2021 (1991). E. J. Tarsa, B. Heying, X. H. Wu, P. Fini, S. P. Den Baars, and J. S. Speck, J. Appl. Phys. 82, 5472 (1997).