HFETor HEMTor TEGFET

Hey guyz  Do you understander what the title of this post? if you don't  i will explain it .
The tittle of this post is HFET i.e  Hetrojunction Field effect transistor .The reason i have written so many names because of this HFET i.e hetrojunction FET is called by so many names such as  HEMT i.e High electron mobility transistor or TEGFET i.e two Dimensional electron Gas FET.
 It is an High speed semiconductor device.
 A potential is formed at junction of two dissimilar semiconductors like Aluminium Gallium Arsenide or Gallium arsenide (AlGaAs/GaAs), where Ef  is higher than the occupation levels of the electrons in the conduction band
The electrons accumulated in this potential well and form a sheet of electron similar to the inversion layer in a MOS structure. The thickness of this sheet is les or equal to 10nm(nano meters ), smaller than the De-broglie wavelength of the electron in that material. This sheet of free electrons behaves like free atoms in a gas and hence it is called electron gas..

In this structure:            

at 2k
                        
This structure is similar to FET with 2DEG(Two Dimentional Electron Gas )as channel.
Application of a bias voltage to gate modulates charges in the 2DEG and thus channel conducts current, this is similar to FET which is faster than MESFET operation. The formation of 2DEG is shown in Fig 1

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