GaN Based Nanotransistors for High Power Applications

_Nowadays the needs for high speed, long distance wireless internet connections, sattelite communications and high frequency radars are   increasing. _These requirements pushes the enginners to design high frequency and high power amplifiers, oscillators and some other high frequency   circuits. Most _of the manifacturers uses  GaAs and InGaP transistors to meet the requiements. But especially for high power circuits enginners should use   multiple _transistor tophologies in these amplifiers and this couses the design to be much complicated and hard to manifacture. These difficulties forces the   manifacturers, research centers and universities to work on new matterials like GaN and / or AlGaN to fulfill these needs.

_As GaN and AlGaN has high breakdown and high electron velocity properties, these matterials are really good candidates for high power and   high _frequency devices, especially for the transistors. You can find a table comparing some properties of different matterials:

  And the leading properties of GaN and AlGaN based nanotransistors can be seen in following figure:

  Figure1: Leading properties of GaN nanotransistors

_These GaN nanotransistors are used for especially high power and high frequency RF circuits. Radars, wireless communication systems, sattelite   communication systems. Nowadays these nanotransistors are used in 3rd generation GSM base stations  because of their high power capability. Also   these transistors have very good noise properties so these transistorsa re used in radiotelescopes. As the days go by the applications are growing. In a   short time period we will use these nanotransistors in our everyday life.

_We as Nanotechnology Research Center, grow our own GaN nanotransistor structures by using our MOCVD system and make the fabrication   and _characterization of these  nanotransistors. (Thanks to Dr. Hongbo Yu for wafers) The startegy is determining a structure and make a fabrication on   the _grown wafer. The characterization measurement results of fabricated nanotransistors gives feedback to Dr Yu for improving the quality of the wafer   or _modify the structure.

_The fabrication includes several steps. Defining the active device areas by etching, preparing contacts by metal deposition by evaporation,   annealing _and passivation are the process steps.  You can see some pictures of nanotransistors which are fabricated in our resaerch laboratories.

  After this fabrication we characterize our nanotransistors. Reducing contact resistance is quite important in transistor fabrication. So first of all we make   the contact resistance measurements on our samples. After contact resistance measurements we start the IV measurements of transistors. The method to   get an IV curve is applying a voltage to gate and sweeping the voltage on drain and measuring the source – drain current.

_Its been a short time that we started to fabricate these nanotransistors but we have some world average results in hand. We have some other   device _designs which are waiting for fabrication. Stay tuned for new pictures of new design devices.

_In near future we will fabricate and characterize some high frequency and some high power devices We stil can make all the DC tests on the   devices _and in a very short time we will start to make the AC characterization of the transistors.

    Nanophotonic Light Sources at UV Wavelengths

 

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

 

    MOCVD Growth, Fabrication and Characterization of Nanophotonic

 

    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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