1. High electron mobility transistors (HEMT) AMIR ABDURAHIM EE4611 04/11/2016

2. Introduction Is a FET Uses Hetero-junction instead of PN junction Uses high mobility materials (GaAs/AlGaAs, GaN/AlGaN, III-V) Small gate-to-channel separation to keep capacitance and drift time to minimum

3. Introduction (continue)  Optimum performance at 30– 300GHZ  Often used in high gain, low noise applications  Works best under high temperature (269c)  GaN HEMT works best for high power applications due to its high band gap  InP is super low noise transistor. Fastest transistor in the world (Cut off at 500GHZ)

4. Potential Applications  Satellite communication  Wireless communication  TV signals  Cellphones  Radars  radio astronomy

5. Before HEMT (GaAs MESFET)  GaAs MESFET  Used in high frequency applications  GaAs preferred due to its high carrier mobility  Si was replaced by GaAs  Was used in application such as RF amplifiers

6. GaAs MESFET  GaAs semiconducting layer has to be doped to ensure that the electrons are mobile  This created a problem of electrons collision with impurities  The collision degraded the high mobility of GaAs

7. HEMT  GaAs/AlGaAs  Hetero-juction: junction between two materials with 2 different band gap  forms a two dimensional electron gas (2-deg) along the GaAs  Conduction Channel along GaAs

8. HEMT

9. HEMT (energy band interface)  Electrons trapped in the quantum well due to band gap difference  It can accumulate up to 10^12/cm^2 in a thin layer of <900nm  No depletion since AlGaAs is fully depleted under normal condition

10. HEMT (energy band interface)  Creation of quantum well

11. Summary and Conclusion  HEMT uses Hetero-junction instead of PN junction  Used in high bandwidth, low noise and high power applications  Small gate-to-channel separation to keep capacitance and drift time to minimum  Electrons accumulate in the conduction channel as 2 dimensional electron gas (2-DEG)  HEMT has the ability to locate a large electron density in a thin layer (<900nm)  High electron mobility and maximum electron velocity in GaAs makes more applicable than MESFET

12. Work cited  Pal, Gyan Prakash, and Anuj Kumar Shrivastav. "International Journal of Scientific and Engineering Research." International Journal of Scientific Research Engineering &Technology (IJSRET) (2012): 43+. Web. 08 Apr. 2016.  Poole, Ian. "HEMT, High Electron Mobility Transistor Tutorial." What Is a HEMT. Adrio Communications Ltd. Web. 08 Apr. 2016.  Poole, Ian. "GaAs FET MESFET Tutorial." MESFET / GaAs FET| MEtal Semiconductor FET / Gallium Arsenide. Adrio Communications Ltd. Web. 08 Apr. 2016.  Zhaojun Liu, Tongde Huang, Qiang Li, Xing Lu, and Xinbo Zou Synthesis Lectures on Emerging Engineering Technologies 2016 2:3, 1-73

13. Five concepts  HEMT is a Field transistor  HEMT uses Hetero-junction rather than PN junction  Small gate-to-channel separation to keep capacitance and drift time to minimum  HEMT used for high gain and low noise applications  Works best under high temperature