GaN/AlGaN DEVICES

LOW DARK CURRENT Al_xGa_1-xN METAL-SEMICONDUCTOR-METAL PHOTODETECTOR

_We are currently interested in AlGaN based photoconductive devices for solar blind and deep UV light detection applications. Namely designing,   fabricating and characterizing Metal-Semiconductor-Metal detector structures. Our aim is to achieve very low dark current, high detectivity, low noise   and high speed detectors.

  AlGaN based devices have proved their potential for UV detection applications [a-b]. AlGaN material has itself high bandgap and it shows high   resistivity. These are good properties for both UV detection and low dark current levels as a bulk material. People are working on different kinds of   detectors on this material. MSM photodetectors are exceptionally attractive as it is easy to obtain high quality Schottky contacts on AlGaN layers.

  MSM devices are basically consists of two Schottky contacts and a semiconductor material in between (See figure).

  When light sent upon to semiconductor it generates electron-hole pairs in it and by applying electric field between the probes we basically collect   electrons and holes so that we had a current circulating in the circuit. If there is no light, there is too little current namely so called current in the circuit   since semiconductor has high resistivity. Dark current is due to thermal excitations of electrons in the material. So basically the minimum power of UV   light detectable by the device is limited by dark current. If one can achieve very low dark current levels then one can in principle count the photons as   they strike.

_ We are designing and growing high quality AlGaN thin films on sapphire substrates using MOCVD technique. Then we are fabricating the devices   using 4 step standard microwave compatible fabrication techniques in Class-100 clean room environment. After fabrication we apply a number of tests   to get I-V, spectral responsivity, noise and high speed characterizations of the devices.

     Here are some fabricated device micrographs.

.   Here are some of the results of our detectors.

     

  References:

  Walker, D., Zhang, X., Kung, P., Saxler, A., Javapour, S., Xu, J., and Razeghi, M.: ‘AlGaN ultraviolet photoconductors grown on sapphire’, Appl. Phys. Lett., 1996, 68, pp.   2100–2101

  Lim, B.W., Chen, Q.C., Yang, J.Y., and Khan, M.A.: ‘High responsivity intrinsic photoconductors based on AlxGa1_xN’, Appl. Phys. Lett., 1996, 68, pp. 3761–3762

 

  Related Groups:

  Necmi Biyikli, Ibrahim Kimukin, Turgut Tut, Orhan Aytur, and Ekmel Ozbay, "Fabrication and characterization of solar-blind Al_0.6Ga_0.4N MSM photodetectors,", Electronic   Letters, volume 41, (2005).

  Necmi Biyikli, Tolga Kartaloglu, Orhan Aytur, Ibrahim Kimukin, and Ekmel Ozbay “High-speed solar-blind AlGaN-based metal–semiconductor–metal photodetectors,”   Physica Status Solid (C), vol.7, 2314–2317 (2003).

     

   Nanophotonic Light Sources at UV Wavelengths

   MOCVD Growth of High-Al Content P-Type AlGaN on AlN/Sapphire Template

 

   Solar-Blind AlGaN Avalanche Photodiodes

 

   Low Dark-Current AlGaN MSM Photodiotes

 

   GaN Based Nanotransistors for High Power Applications

 

   Fabrication and Characterization of GaN Based LEDs

Metamaterials   -    Photonic Crystals  -  GaN/AlGaN Devices  -  Other Semiconductor Devices and Fabrication Techniques

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